Currently used hrtimer_try_to_cancel() is racy:
raw_spin_lock(&rq->lock)
... dl_task_timer raw_spin_lock(&rq->lock)
... raw_spin_lock(&rq->lock) ...
switched_from_dl() ... ...
hrtimer_try_to_cancel() ... ...
switched_to_fair() ... ...
... ... ...
... ... ...
raw_spin_unlock(&rq->lock) ... (asquired)
... ... ...
... ... ...
do_exit() ... ...
schedule() ... ...
raw_spin_lock(&rq->lock) ... raw_spin_unlock(&rq->lock)
... ... ...
raw_spin_unlock(&rq->lock) ... raw_spin_lock(&rq->lock)
... ... (asquired)
put_task_struct() ... ...
free_task_struct() ... ...
... ... raw_spin_unlock(&rq->lock)
... (asquired) ...
... ... ...
... (use after free) ...
So, let's implement 100% guaranteed way to cancel the timer and let's
be sure we are safe even in very unlikely situations.
rq unlocking does not limit the area of switched_from_dl() use, because
this has already been possible in pull_dl_task() below.
Let's consider the safety of of this unlocking. New code in the patch
is working when hrtimer_try_to_cancel() fails. This means the callback
is running. In this case hrtimer_cancel() is just waiting till the
callback is finished. Two
1) Since we are in switched_from_dl(), new class is not dl_sched_class and
new prio is not less MAX_DL_PRIO. So, the callback returns early; it's
right after !dl_task() check. After that hrtimer_cancel() returns back too.
The above is:
raw_spin_lock(rq->lock); ...
... dl_task_timer()
... raw_spin_lock(rq->lock);
switched_from_dl() ...
hrtimer_try_to_cancel() ...
raw_spin_unlock(rq->lock); ...
hrtimer_cancel() ...
... raw_spin_unlock(rq->lock);
... return HRTIMER_NORESTART;
... ...
raw_spin_lock(rq->lock); ...
2) But the below is also possible:
dl_task_timer()
raw_spin_lock(rq->lock);
...
raw_spin_unlock(rq->lock);
raw_spin_lock(rq->lock); ...
switched_from_dl() ...
hrtimer_try_to_cancel() ...
... return HRTIMER_NORESTART;
raw_spin_unlock(rq->lock); ...
hrtimer_cancel(); ...
raw_spin_lock(rq->lock); ...
In this case hrtimer_cancel() returns immediately. Very unlikely case,
just to mention.
Nobody can manipulate the task, because check_class_changed() is
always called with pi_lock locked. Nobody can force the task to
participate in (concurrent) priority inheritance schemes (the same reason).
All concurrent task operations require pi_lock, which is held by us.
No deadlocks with dl_task_timer() are possible, because it returns
right after !dl_task() check (it does nothing).
If we receive a new dl_task during the time of unlocked rq, we just
don't have to do pull_dl_task() in switched_from_dl() further.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
[ Added comments]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1414420852.19914.186.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In some cases this can trigger a true flood of output.
Requested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The kauditd_thread wait loop is a bit iffy; it has a number of problems:
- calls try_to_freeze() before schedule(); you typically want the
thread to re-evaluate the sleep condition when unfreezing, also
freeze_task() issues a wakeup.
- it unconditionally does the {add,remove}_wait_queue(), even when the
sleep condition is false.
Use wait_event_freezable() that does the right thing.
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Eric Paris <eparis@redhat.com>
Cc: oleg@redhat.com
Cc: Eric Paris <eparis@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141002102251.GA6324@worktop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
There is a race between kthread_stop() and the new wait_woken() that
can result in a lack of progress.
CPU 0 | CPU 1
|
rfcomm_run() | kthread_stop()
... |
if (!test_bit(KTHREAD_SHOULD_STOP)) |
| set_bit(KTHREAD_SHOULD_STOP)
| wake_up_process()
wait_woken() | wait_for_completion()
set_current_state(INTERRUPTIBLE) |
if (!WQ_FLAG_WOKEN) |
schedule_timeout() |
|
After which both tasks will wait.. forever.
Fix this by having wait_woken() check for kthread_should_stop() but
only for kthreads (obviously).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
cond_resched() is a preemption point, not strictly a blocking
primitive, so exclude it from the ->state test.
In particular, preemption preserves task_struct::state.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: oleg@redhat.com
Cc: Alex Elder <alex.elder@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Axel Lin <axel.lin@ingics.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20140924082242.656559952@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Validate we call might_sleep() with TASK_RUNNING, which catches places
where we nest blocking primitives, eg. mutex usage in a wait loop.
Since all blocking is arranged through task_struct::state, nesting
this will cause the inner primitive to set TASK_RUNNING and the outer
will thus not block.
Another observed problem is calling a blocking function from
schedule()->sched_submit_work()->blk_schedule_flush_plug() which will
then destroy the task state for the actual __schedule() call that
comes after it.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: oleg@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140924082242.591637616@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This is a genuine bug in add_unformed_module(), we cannot use blocking
primitives inside a wait loop.
So rewrite the wait_event_interruptible() usage to use the fresh
wait_woken() stuff.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: oleg@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: http://lkml.kernel.org/r/20140924082242.458562904@infradead.org
[ So this is probably complex to backport and the race wasn't reported AFAIK,
so not marked for -stable. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
smp_hotplug_thread::{setup,unpark} functions can sleep too, so be
consistent and do the same for all callbacks.
__might_sleep+0x74/0x80
kmem_cache_alloc_trace+0x4e/0x1c0
perf_event_alloc+0x55/0x450
perf_event_create_kernel_counter+0x2f/0x100
watchdog_nmi_enable+0x8d/0x160
watchdog_enable+0x45/0x90
smpboot_thread_fn+0xec/0x2b0
kthread+0xe4/0x100
ret_from_fork+0x7c/0xb0
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: oleg@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140924082242.392279328@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
do_wait() is a big wait loop, but we set TASK_RUNNING too late; we end
up calling potential sleeps before we reset it.
Not strictly a bug since we're guaranteed to exit the loop and not
call schedule(); put in annotations to quiet might_sleep().
WARNING: CPU: 0 PID: 1 at ../kernel/sched/core.c:7123 __might_sleep+0x7e/0x90()
do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff8109a788>] do_wait+0x88/0x270
Call Trace:
[<ffffffff81694991>] dump_stack+0x4e/0x7a
[<ffffffff8109877c>] warn_slowpath_common+0x8c/0xc0
[<ffffffff8109886c>] warn_slowpath_fmt+0x4c/0x50
[<ffffffff810bca6e>] __might_sleep+0x7e/0x90
[<ffffffff811a1c15>] might_fault+0x55/0xb0
[<ffffffff8109a3fb>] wait_consider_task+0x90b/0xc10
[<ffffffff8109a804>] do_wait+0x104/0x270
[<ffffffff8109b837>] SyS_wait4+0x77/0x100
[<ffffffff8169d692>] system_call_fastpath+0x16/0x1b
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: umgwanakikbuti@gmail.com
Cc: ilya.dryomov@inktank.com
Cc: Alex Elder <alex.elder@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Axel Lin <axel.lin@ingics.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Guillaume Morin <guillaume@morinfr.org>
Cc: Ionut Alexa <ionut.m.alexa@gmail.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Michal Schmidt <mschmidt@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20140924082242.186408915@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
There are a few places that call blocking primitives from wait loops,
provide infrastructure to support this without the typical
task_struct::state collision.
We record the wakeup in wait_queue_t::flags which leaves
task_struct::state free to be used by others.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140924082242.051202318@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We're going to make might_sleep() test for TASK_RUNNING, because
blocking without TASK_RUNNING will destroy the task state by setting
it to TASK_RUNNING.
There are a few occasions where its 'valid' to call blocking
primitives (and mutex_lock in particular) and not have TASK_RUNNING,
typically such cases are right before we set TASK_RUNNING anyhow.
Robustify the code by not assuming this; this has the beneficial side
effect of allowing optional code emission for fixing the above
might_sleep() false positives.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140924082241.988560063@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Use nr_cpus_allowed to bail from select_task_rq() when only one cpu
can be used, and saves some cycles for pinned tasks.
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413253360-5318-2-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
There is no need to do balance during fork since SCHED_DEADLINE
tasks can't fork. This patch avoid the SD_BALANCE_FORK check.
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1413253360-5318-1-git-send-email-wanpeng.li@linux.intel.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
How we deal with updates to exclusive cpusets is currently broken.
As an example, suppose we have an exclusive cpuset composed of
two cpus: A[cpu0,cpu1]. We can assign SCHED_DEADLINE task to it
up to the allowed bandwidth. If we want now to modify cpusetA's
cpumask, we have to check that removing a cpu's amount of
bandwidth doesn't break AC guarantees. This thing isn't checked
in the current code.
This patch fixes the problem above, denying an update if the
new cpumask won't have enough bandwidth for SCHED_DEADLINE tasks
that are currently active.
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: cgroups@vger.kernel.org
Link: http://lkml.kernel.org/r/5433E6AF.5080105@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Exclusive cpusets are the only way users can restrict SCHED_DEADLINE tasks
affinity (performing what is commonly called clustered scheduling).
Unfortunately, such thing is currently broken for two reasons:
- No check is performed when the user tries to attach a task to
an exlusive cpuset (recall that exclusive cpusets have an
associated maximum allowed bandwidth).
- Bandwidths of source and destination cpusets are not correctly
updated after a task is migrated between them.
This patch fixes both things at once, as they are opposite faces
of the same coin.
The check is performed in cpuset_can_attach(), as there aren't any
points of failure after that function. The updated is split in two
halves. We first reserve bandwidth in the destination cpuset, after
we pass the check in cpuset_can_attach(). And we then release
bandwidth from the source cpuset when the task's affinity is
actually changed. Even if there can be time windows when sched_setattr()
may erroneously fail in the source cpuset, we are fine with it, as
we can't perfom an atomic update of both cpusets at once.
Reported-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Reported-by: Vincent Legout <vincent@legout.info>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dario Faggioli <raistlin@linux.it>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Cc: Fabio Checconi <fchecconi@gmail.com>
Cc: michael@amarulasolutions.com
Cc: luca.abeni@unitn.it
Cc: Li Zefan <lizefan@huawei.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Link: http://lkml.kernel.org/r/1411118561-26323-3-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
As Kirill mentioned (https://lkml.org/lkml/2013/1/29/118):
| If rq has already had 2 or more pushable tasks and we try to add a
| pinned task then call of push_rt_task will just waste a time.
Just switched pinned task is not able to be pushed. If the rq has had
several dl tasks before they have already been considered as candidates
to be pushed (or pulled). This patch implements the same behavior as rt
class which introduced by commit 1044791755 ("sched/rt: Do not try to
push tasks if pinned task switches to RT").
Suggested-by: Kirill V Tkhai <tkhai@yandex.ru>
Acked-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413938203-224610-1-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
task_preempt_count() is pointless if preemption counter is per-cpu,
currently this is x86 only. It is only valid if the task is not
running, and even in this case the only info it can provide is the
state of PREEMPT_ACTIVE bit.
Change its single caller to check p->on_rq instead, this should be
the same if p->state != TASK_RUNNING, and kill this helper.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Alexander Graf <agraf@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/20141008183348.GC17495@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Both callers of finish_task_switch() need to recalculate this_rq()
and pass it as an argument, plus __schedule() does this again after
context_switch().
It would be simpler to call this_rq() once in finish_task_switch()
and return the this rq to the callers.
Note: probably "int cpu" in __schedule() should die; it is not used
and both rcu_note_context_switch() and wq_worker_sleeping() do not
really need this argument.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141009193232.GB5408@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
finish_task_switch() enables preemption, so post_schedule(rq) can be
called on the wrong (and even dead) CPU. Afaics, nothing really bad
can happen, but in this case we can wrongly clear rq->post_schedule
on that CPU. And this simply looks wrong in any case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141008193644.GA32055@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In pseudo-interleaved numa_groups, all tasks try to relocate to
the group's preferred_nid. When a group is spread across multiple
NUMA nodes, this can lead to tasks swapping their location with
other tasks inside the same group, instead of swapping location with
tasks from other NUMA groups. This can keep NUMA groups from converging.
Examining all nodes, when dealing with a task in a pseudo-interleaved
NUMA group, avoids this problem. Note that only CPUs in nodes that
improve the task or group score are examined, so the loop isn't too
bad.
Tested-by: Vinod Chegu <chegu_vinod@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: "Vinod Chegu" <chegu_vinod@hp.com>
Cc: mgorman@suse.de
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141009172747.0d97c38c@annuminas.surriel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
On systems with complex NUMA topologies, the node scoring is adjusted
to allow workloads to converge on nodes that are near each other.
The way a task group's preferred nid is determined needs to be adjusted,
in order for the preferred_nid to be consistent with group_weight scoring.
This ensures that we actually try to converge workloads on adjacent nodes.
Signed-off-by: Rik van Riel <riel@redhat.com>
Tested-by: Chegu Vinod <chegu_vinod@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413530994-9732-6-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In order to do task placement on systems with complex NUMA topologies,
it is necessary to count the faults on nodes nearby the node that is
being examined for a potential move.
In case of a system with a backplane interconnect, we are dealing with
groups of NUMA nodes; each of the nodes within a group is the same number
of hops away from nodes in other groups in the system. Optimal placement
on this topology is achieved by counting all nearby nodes equally. When
comparing nodes A and B at distance N, nearby nodes are those at distances
smaller than N from nodes A or B.
Placement strategy on a system with a glueless mesh NUMA topology needs
to be different, because there are no natural groups of nodes determined
by the hardware. Instead, when dealing with two nodes A and B at distance
N, N >= 2, there will be intermediate nodes at distance < N from both nodes
A and B. Good placement can be achieved by right shifting the faults on
nearby nodes by the number of hops from the node being scored. In this
context, a nearby node is any node less than the maximum distance in the
system away from the node. Those nodes are skipped for efficiency reasons,
there is no real policy reason to do so.
Placement policy on directly connected NUMA systems is not affected.
Signed-off-by: Rik van Riel <riel@redhat.com>
Tested-by: Chegu Vinod <chegu_vinod@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Link: http://lkml.kernel.org/r/1413530994-9732-5-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Preparatory patch for adding NUMA placement on systems with
complex NUMA topology. Also fix a potential divide by zero
in group_weight()
Signed-off-by: Rik van Riel <riel@redhat.com>
Tested-by: Chegu Vinod <chegu_vinod@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413530994-9732-4-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Smaller NUMA systems tend to have all NUMA nodes directly connected
to each other. This includes the degenerate case of a system with just
one node, ie. a non-NUMA system.
Larger systems can have two kinds of NUMA topology, which affects how
tasks and memory should be placed on the system.
On glueless mesh systems, nodes that are not directly connected to
each other will bounce traffic through intermediary nodes. Task groups
can be run closer to each other by moving tasks from a node to an
intermediary node between it and the task's preferred node.
On NUMA systems with backplane controllers, the intermediary hops
are incapable of running programs. This creates "islands" of nodes
that are at an equal distance to anywhere else in the system.
Each kind of topology requires a slightly different placement
algorithm; this patch provides the mechanism to detect the kind
of NUMA topology of a system.
Signed-off-by: Rik van Riel <riel@redhat.com>
Tested-by: Chegu Vinod <chegu_vinod@hp.com>
[ Changed to use kernel/sched/sched.h ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Link: http://lkml.kernel.org/r/1413530994-9732-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Export some information that is necessary to do placement of
tasks on systems with multi-level NUMA topologies.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413530994-9732-2-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1) switched_to_dl() check is wrong. We reschedule only
if rq->curr is deadline task, and we do not reschedule
if it's a lower priority task. But we must always
preempt a task of other classes.
2) dl_task_timer():
Policy does not change in case of priority inheritance.
rt_mutex_setprio() changes prio, while policy remains old.
So we lose some balancing logic in dl_task_timer() and
switched_to_dl() when we check policy instead of priority. Boosted
task may be rq->curr.
(I didn't change switched_from_dl() because no check is necessary
there at all).
I've looked at this place(switched_to_dl) several times and even fixed
this function, but found just now... I suppose some performance tests
may work better after this.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413909356.19914.128.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>
preempt_schedule_context() does preempt_enable_notrace() at the end
and this can call the same function again; exception_exit() is heavy
and it is quite possible that need-resched is true again.
1. Change this code to dec preempt_count() and check need_resched()
by hand.
2. As Linus suggested, we can use the PREEMPT_ACTIVE bit and avoid
the enable/disable dance around __schedule(). But in this case
we need to move into sched/core.c.
3. Cosmetic, but x86 forgets to declare this function. This doesn't
really matter because it is only called by asm helpers, still it
make sense to add the declaration into asm/preempt.h to match
preempt_schedule().
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Graf <agraf@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Chuck Ebbert <cebbert.lkml@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20141005202322.GB27962@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
While offling node by hot removing memory, the following divide error
occurs:
divide error: 0000 [#1] SMP
[...]
Call Trace:
[...] handle_mm_fault
[...] ? try_to_wake_up
[...] ? wake_up_state
[...] __do_page_fault
[...] ? do_futex
[...] ? put_prev_entity
[...] ? __switch_to
[...] do_page_fault
[...] page_fault
[...]
RIP [<ffffffff810a7081>] task_numa_fault
RSP <ffff88084eb2bcb0>
The issue occurs as follows:
1. When page fault occurs and page is allocated from node 1,
task_struct->numa_faults_buffer_memory[] of node 1 is
incremented and p->numa_faults_locality[] is also incremented
as follows:
o numa_faults_buffer_memory[] o numa_faults_locality[]
NR_NUMA_HINT_FAULT_TYPES
| 0 | 1 |
---------------------------------- ----------------------
node 0 | 0 | 0 | remote | 0 |
node 1 | 0 | 1 | locale | 1 |
---------------------------------- ----------------------
2. node 1 is offlined by hot removing memory.
3. When page fault occurs, fault_types[] is calculated by using
p->numa_faults_buffer_memory[] of all online nodes in
task_numa_placement(). But node 1 was offline by step 2. So
the fault_types[] is calculated by using only
p->numa_faults_buffer_memory[] of node 0. So both of fault_types[]
are set to 0.
4. The values(0) of fault_types[] pass to update_task_scan_period().
5. numa_faults_locality[1] is set to 1. So the following division is
calculated.
static void update_task_scan_period(struct task_struct *p,
unsigned long shared, unsigned long private){
...
ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared));
}
6. But both of private and shared are set to 0. So divide error
occurs here.
The divide error is rare case because the trigger is node offline.
This patch always increments denominator for avoiding divide error.
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/54475703.8000505@jp.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Unlocked access to dst_rq->curr in task_numa_compare() is racy.
If curr task is exiting this may be a reason of use-after-free:
task_numa_compare() do_exit()
... current->flags |= PF_EXITING;
... release_task()
... ~~delayed_put_task_struct()~~
... schedule()
rcu_read_lock() ...
cur = ACCESS_ONCE(dst_rq->curr) ...
... rq->curr = next;
... context_switch()
... finish_task_switch()
... put_task_struct()
... __put_task_struct()
... free_task_struct()
task_numa_assign() ...
get_task_struct() ...
As noted by Oleg:
<<The lockless get_task_struct(tsk) is only safe if tsk == current
and didn't pass exit_notify(), or if this tsk was found on a rcu
protected list (say, for_each_process() or find_task_by_vpid()).
IOW, it is only safe if release_task() was not called before we
take rcu_read_lock(), in this case we can rely on the fact that
delayed_put_pid() can not drop the (potentially) last reference
until rcu_read_unlock().
And as Kirill pointed out task_numa_compare()->task_numa_assign()
path does get_task_struct(dst_rq->curr) and this is not safe. The
task_struct itself can't go away, but rcu_read_lock() can't save
us from the final put_task_struct() in finish_task_switch(); this
reference goes away without rcu gp>>
The patch provides simple check of PF_EXITING flag. If it's not set,
this guarantees that call_rcu() of delayed_put_task_struct() callback
hasn't happened yet, so we can safely do get_task_struct() in
task_numa_assign().
Locked dst_rq->lock protects from concurrency with the last schedule().
Reusing or unmapping of cur's memory may happen without it.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413962231.19914.130.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>
dl_task_timer() is racy against several paths. Daniel noticed that
the replenishment timer may experience a race condition against an
enqueue_dl_entity() called from rt_mutex_setprio(). With his own
words:
rt_mutex_setprio() resets p->dl.dl_throttled. So the pattern is:
start_dl_timer() throttled = 1, rt_mutex_setprio() throlled = 0,
sched_switch() -> enqueue_task(), dl_task_timer-> enqueue_task()
throttled is 0
=> BUG_ON(on_dl_rq(dl_se)) fires as the scheduling entity is already
enqueued on the -deadline runqueue.
As we do for the other races, we just bail out in the replenishment
timer code.
Reported-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Tested-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: vincent@legout.info
Cc: Dario Faggioli <raistlin@linux.it>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Cc: Fabio Checconi <fchecconi@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1414142198-18552-5-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In the deboost path, right after the dl_boosted flag has been
reset, we can currently end up replenishing using -deadline
parameters of a !SCHED_DEADLINE entity. This of course causes
a bug, as those parameters are empty.
In the case depicted above it is safe to simply bail out, as
the deboosted task is going to be back to its original scheduling
class anyway.
Reported-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Tested-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: vincent@legout.info
Cc: Dario Faggioli <raistlin@linux.it>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Cc: Fabio Checconi <fchecconi@gmail.com>
Link: http://lkml.kernel.org/r/1414142198-18552-4-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The race may happen when somebody is changing task_group of a forking task.
Child's cgroup is the same as parent's after dup_task_struct() (there just
memory copying). Also, cfs_rq and rt_rq are the same as parent's.
But if parent changes its task_group before it's called cgroup_post_fork(),
we do not reflect this situation on child. Child's cfs_rq and rt_rq remain
the same, while child's task_group changes in cgroup_post_fork().
To fix this we introduce fork() method, which calls sched_move_task() directly.
This function changes sched_task_group on appropriate (also its logic has
no problem with freshly created tasks, so we shouldn't introduce something
special; we are able just to use it).
Possibly, this decides the Burke Libbey's problem: https://lkml.org/lkml/2014/10/24/456
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1414405105.19914.169.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Clean up the code in process.c after recent changes to get rid of
unnecessary labels and goto statements.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
as per 0c740d0afc (introduce for_each_thread() to replace the buggy
while_each_thread()) get rid of do_each_thread { } while_each_thread()
construct and replace it by a more error prone for_each_thread.
This patch doesn't introduce any user visible change.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM freezer relies on having all tasks frozen by the time devices are
getting frozen so that no task will touch them while they are getting
frozen. But OOM killer is allowed to kill an already frozen task in
order to handle OOM situtation. In order to protect from late wake ups
OOM killer is disabled after all tasks are frozen. This, however, still
keeps a window open when a killed task didn't manage to die by the time
freeze_processes finishes.
Reduce the race window by checking all tasks after OOM killer has been
disabled. This is still not race free completely unfortunately because
oom_killer_disable cannot stop an already ongoing OOM killer so a task
might still wake up from the fridge and get killed without
freeze_processes noticing. Full synchronization of OOM and freezer is,
however, too heavy weight for this highly unlikely case.
Introduce and check oom_kills counter which gets incremented early when
the allocator enters __alloc_pages_may_oom path and only check all the
tasks if the counter changes during the freezing attempt. The counter
is updated so early to reduce the race window since allocator checked
oom_killer_disabled which is set by PM-freezing code. A false positive
will push the PM-freezer into a slow path but that is not a big deal.
Changes since v1
- push the re-check loop out of freeze_processes into
check_frozen_processes and invert the condition to make the code more
readable as per Rafael
Fixes: f660daac47 (oom: thaw threads if oom killed thread is frozen before deferring)
Cc: 3.2+ <stable@vger.kernel.org> # 3.2+
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
__thaw_task() no longer clears frozen flag since commit a3201227f8
(freezer: make freezing() test freeze conditions in effect instead of TIF_FREEZE).
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Since f660daac47 (oom: thaw threads if oom killed thread is frozen
before deferring) OOM killer relies on being able to thaw a frozen task
to handle OOM situation but a3201227f8 (freezer: make freezing() test
freeze conditions in effect instead of TIF_FREEZE) has reorganized the
code and stopped clearing freeze flag in __thaw_task. This means that
the target task only wakes up and goes into the fridge again because the
freezing condition hasn't changed for it. This reintroduces the bug
fixed by f660daac47.
Fix the issue by checking for TIF_MEMDIE thread flag in
freezing_slow_path and exclude the task from freezing completely. If a
task was already frozen it would get woken by __thaw_task from OOM killer
and get out of freezer after rechecking freezing().
Changes since v1
- put TIF_MEMDIE check into freezing_slowpath rather than in __refrigerator
as per Oleg
- return __thaw_task into oom_scan_process_thread because
oom_kill_process will not wake task in the fridge because it is
sleeping uninterruptible
[mhocko@suse.cz: rewrote the changelog]
Fixes: a3201227f8 (freezer: make freezing() test freeze conditions in effect instead of TIF_FREEZE)
Cc: 3.3+ <stable@vger.kernel.org> # 3.3+
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Pull audit updates from Eric Paris:
"So this change across a whole bunch of arches really solves one basic
problem. We want to audit when seccomp is killing a process. seccomp
hooks in before the audit syscall entry code. audit_syscall_entry
took as an argument the arch of the given syscall. Since the arch is
part of what makes a syscall number meaningful it's an important part
of the record, but it isn't available when seccomp shoots the
syscall...
For most arch's we have a better way to get the arch (syscall_get_arch)
So the solution was two fold: Implement syscall_get_arch() everywhere
there is audit which didn't have it. Use syscall_get_arch() in the
seccomp audit code. Having syscall_get_arch() everywhere meant it was
a useless flag on the stack and we could get rid of it for the typical
syscall entry.
The other changes inside the audit system aren't grand, fixed some
records that had invalid spaces. Better locking around the task comm
field. Removing some dead functions and structs. Make some things
static. Really minor stuff"
* git://git.infradead.org/users/eparis/audit: (31 commits)
audit: rename audit_log_remove_rule to disambiguate for trees
audit: cull redundancy in audit_rule_change
audit: WARN if audit_rule_change called illegally
audit: put rule existence check in canonical order
next: openrisc: Fix build
audit: get comm using lock to avoid race in string printing
audit: remove open_arg() function that is never used
audit: correct AUDIT_GET_FEATURE return message type
audit: set nlmsg_len for multicast messages.
audit: use union for audit_field values since they are mutually exclusive
audit: invalid op= values for rules
audit: use atomic_t to simplify audit_serial()
kernel/audit.c: use ARRAY_SIZE instead of sizeof/sizeof[0]
audit: reduce scope of audit_log_fcaps
audit: reduce scope of audit_net_id
audit: arm64: Remove the audit arch argument to audit_syscall_entry
arm64: audit: Add audit hook in syscall_trace_enter/exit()
audit: x86: drop arch from __audit_syscall_entry() interface
sparc: implement is_32bit_task
sparc: properly conditionalize use of TIF_32BIT
...
Commit b0c29f79ec (futexes: Avoid taking the hb->lock if there's
nothing to wake up) changes the futex code to avoid taking a lock when
there are no waiters. This code has been subsequently fixed in commit
11d4616bd0 (futex: revert back to the explicit waiter counting code).
Both the original commit and the fix-up rely on get_futex_key_refs() to
always imply a barrier.
However, for private futexes, none of the cases in the switch statement
of get_futex_key_refs() would be hit and the function completes without
a memory barrier as required before checking the "waiters" in
futex_wake() -> hb_waiters_pending(). The consequence is a race with a
thread waiting on a futex on another CPU, allowing the waker thread to
read "waiters == 0" while the waiter thread to have read "futex_val ==
locked" (in kernel).
Without this fix, the problem (user space deadlocks) can be seen with
Android bionic's mutex implementation on an arm64 multi-cluster system.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Matteo Franchin <Matteo.Franchin@arm.com>
Fixes: b0c29f79ec (futexes: Avoid taking the hb->lock if there's nothing to wake up)
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Tested-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: <stable@vger.kernel.org>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull percpu consistent-ops changes from Tejun Heo:
"Way back, before the current percpu allocator was implemented, static
and dynamic percpu memory areas were allocated and handled separately
and had their own accessors. The distinction has been gone for many
years now; however, the now duplicate two sets of accessors remained
with the pointer based ones - this_cpu_*() - evolving various other
operations over time. During the process, we also accumulated other
inconsistent operations.
This pull request contains Christoph's patches to clean up the
duplicate accessor situation. __get_cpu_var() uses are replaced with
with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr().
Unfortunately, the former sometimes is tricky thanks to C being a bit
messy with the distinction between lvalues and pointers, which led to
a rather ugly solution for cpumask_var_t involving the introduction of
this_cpu_cpumask_var_ptr().
This converts most of the uses but not all. Christoph will follow up
with the remaining conversions in this merge window and hopefully
remove the obsolete accessors"
* 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits)
irqchip: Properly fetch the per cpu offset
percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix
ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write.
percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t
Revert "powerpc: Replace __get_cpu_var uses"
percpu: Remove __this_cpu_ptr
clocksource: Replace __this_cpu_ptr with raw_cpu_ptr
sparc: Replace __get_cpu_var uses
avr32: Replace __get_cpu_var with __this_cpu_write
blackfin: Replace __get_cpu_var uses
tile: Use this_cpu_ptr() for hardware counters
tile: Replace __get_cpu_var uses
powerpc: Replace __get_cpu_var uses
alpha: Replace __get_cpu_var
ia64: Replace __get_cpu_var uses
s390: cio driver &__get_cpu_var replacements
s390: Replace __get_cpu_var uses
mips: Replace __get_cpu_var uses
MIPS: Replace __get_cpu_var uses in FPU emulator.
arm: Replace __this_cpu_ptr with raw_cpu_ptr
...
A panic was seen in the following sitation.
There are two threads running on the system. The first thread is a system
monitoring thread that is reading /proc/modules. The second thread is
loading and unloading a module (in this example I'm using my simple
dummy-module.ko). Note, in the "real world" this occurred with the qlogic
driver module.
When doing this, the following panic occurred:
------------[ cut here ]------------
kernel BUG at kernel/module.c:3739!
invalid opcode: 0000 [#1] SMP
Modules linked in: binfmt_misc sg nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel lrw igb gf128mul glue_helper iTCO_wdt iTCO_vendor_support ablk_helper ptp sb_edac cryptd pps_core edac_core shpchp i2c_i801 pcspkr wmi lpc_ich ioatdma mfd_core dca ipmi_si nfsd ipmi_msghandler auth_rpcgss nfs_acl lockd sunrpc xfs libcrc32c sr_mod cdrom sd_mod crc_t10dif crct10dif_common mgag200 syscopyarea sysfillrect sysimgblt i2c_algo_bit drm_kms_helper ttm isci drm libsas ahci libahci scsi_transport_sas libata i2c_core dm_mirror dm_region_hash dm_log dm_mod [last unloaded: dummy_module]
CPU: 37 PID: 186343 Comm: cat Tainted: GF O-------------- 3.10.0+ #7
Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.00.29.D696.1311111329 11/11/2013
task: ffff8807fd2d8000 ti: ffff88080fa7c000 task.ti: ffff88080fa7c000
RIP: 0010:[<ffffffff810d64c5>] [<ffffffff810d64c5>] module_flags+0xb5/0xc0
RSP: 0018:ffff88080fa7fe18 EFLAGS: 00010246
RAX: 0000000000000003 RBX: ffffffffa03b5200 RCX: 0000000000000000
RDX: 0000000000001000 RSI: ffff88080fa7fe38 RDI: ffffffffa03b5000
RBP: ffff88080fa7fe28 R08: 0000000000000010 R09: 0000000000000000
R10: 0000000000000000 R11: 000000000000000f R12: ffffffffa03b5000
R13: ffffffffa03b5008 R14: ffffffffa03b5200 R15: ffffffffa03b5000
FS: 00007f6ae57ef740(0000) GS:ffff88101e7a0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000404f70 CR3: 0000000ffed48000 CR4: 00000000001407e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Stack:
ffffffffa03b5200 ffff8810101e4800 ffff88080fa7fe70 ffffffff810d666c
ffff88081e807300 000000002e0f2fbf 0000000000000000 ffff88100f257b00
ffffffffa03b5008 ffff88080fa7ff48 ffff8810101e4800 ffff88080fa7fee0
Call Trace:
[<ffffffff810d666c>] m_show+0x19c/0x1e0
[<ffffffff811e4d7e>] seq_read+0x16e/0x3b0
[<ffffffff812281ed>] proc_reg_read+0x3d/0x80
[<ffffffff811c0f2c>] vfs_read+0x9c/0x170
[<ffffffff811c1a58>] SyS_read+0x58/0xb0
[<ffffffff81605829>] system_call_fastpath+0x16/0x1b
Code: 48 63 c2 83 c2 01 c6 04 03 29 48 63 d2 eb d9 0f 1f 80 00 00 00 00 48 63 d2 c6 04 13 2d 41 8b 0c 24 8d 50 02 83 f9 01 75 b2 eb cb <0f> 0b 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41
RIP [<ffffffff810d64c5>] module_flags+0xb5/0xc0
RSP <ffff88080fa7fe18>
Consider the two processes running on the system.
CPU 0 (/proc/modules reader)
CPU 1 (loading/unloading module)
CPU 0 opens /proc/modules, and starts displaying data for each module by
traversing the modules list via fs/seq_file.c:seq_open() and
fs/seq_file.c:seq_read(). For each module in the modules list, seq_read
does
op->start() <-- this is a pointer to m_start()
op->show() <- this is a pointer to m_show()
op->stop() <-- this is a pointer to m_stop()
The m_start(), m_show(), and m_stop() module functions are defined in
kernel/module.c. The m_start() and m_stop() functions acquire and release
the module_mutex respectively.
ie) When reading /proc/modules, the module_mutex is acquired and released
for each module.
m_show() is called with the module_mutex held. It accesses the module
struct data and attempts to write out module data. It is in this code
path that the above BUG_ON() warning is encountered, specifically m_show()
calls
static char *module_flags(struct module *mod, char *buf)
{
int bx = 0;
BUG_ON(mod->state == MODULE_STATE_UNFORMED);
...
The other thread, CPU 1, in unloading the module calls the syscall
delete_module() defined in kernel/module.c. The module_mutex is acquired
for a short time, and then released. free_module() is called without the
module_mutex. free_module() then sets mod->state = MODULE_STATE_UNFORMED,
also without the module_mutex. Some additional code is called and then the
module_mutex is reacquired to remove the module from the modules list:
/* Now we can delete it from the lists */
mutex_lock(&module_mutex);
stop_machine(__unlink_module, mod, NULL);
mutex_unlock(&module_mutex);
This is the sequence of events that leads to the panic.
CPU 1 is removing dummy_module via delete_module(). It acquires the
module_mutex, and then releases it. CPU 1 has NOT set dummy_module->state to
MODULE_STATE_UNFORMED yet.
CPU 0, which is reading the /proc/modules, acquires the module_mutex and
acquires a pointer to the dummy_module which is still in the modules list.
CPU 0 calls m_show for dummy_module. The check in m_show() for
MODULE_STATE_UNFORMED passed for dummy_module even though it is being
torn down.
Meanwhile CPU 1, which has been continuing to remove dummy_module without
holding the module_mutex, now calls free_module() and sets
dummy_module->state to MODULE_STATE_UNFORMED.
CPU 0 now calls module_flags() with dummy_module and ...
static char *module_flags(struct module *mod, char *buf)
{
int bx = 0;
BUG_ON(mod->state == MODULE_STATE_UNFORMED);
and BOOM.
Acquire and release the module_mutex lock around the setting of
MODULE_STATE_UNFORMED in the teardown path, which should resolve the
problem.
Testing: In the unpatched kernel I can panic the system within 1 minute by
doing
while (true) do insmod dummy_module.ko; rmmod dummy_module.ko; done
and
while (true) do cat /proc/modules; done
in separate terminals.
In the patched kernel I was able to run just over one hour without seeing
any issues. I also verified the output of panic via sysrq-c and the output
of /proc/modules looks correct for all three states for the dummy_module.
dummy_module 12661 0 - Unloading 0xffffffffa03a5000 (OE-)
dummy_module 12661 0 - Live 0xffffffffa03bb000 (OE)
dummy_module 14015 1 - Loading 0xffffffffa03a5000 (OE+)
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org
Merge second patch-bomb from Andrew Morton:
- a few hotfixes
- drivers/dma updates
- MAINTAINERS updates
- Quite a lot of lib/ updates
- checkpatch updates
- binfmt updates
- autofs4
- drivers/rtc/
- various small tweaks to less used filesystems
- ipc/ updates
- kernel/watchdog.c changes
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (135 commits)
mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared
kernel/param: consolidate __{start,stop}___param[] in <linux/moduleparam.h>
ia64: remove duplicate declarations of __per_cpu_start[] and __per_cpu_end[]
frv: remove unused declarations of __start___ex_table and __stop___ex_table
kvm: ensure hard lockup detection is disabled by default
kernel/watchdog.c: control hard lockup detection default
staging: rtl8192u: use %*pEn to escape buffer
staging: rtl8192e: use %*pEn to escape buffer
staging: wlan-ng: use %*pEhp to print SN
lib80211: remove unused print_ssid()
wireless: hostap: proc: print properly escaped SSID
wireless: ipw2x00: print SSID via %*pE
wireless: libertas: print esaped string via %*pE
lib/vsprintf: add %*pE[achnops] format specifier
lib / string_helpers: introduce string_escape_mem()
lib / string_helpers: refactoring the test suite
lib / string_helpers: move documentation to c-file
include/linux: remove strict_strto* definitions
arch/x86/mm/numa.c: fix boot failure when all nodes are hotpluggable
fs: check bh blocknr earlier when searching lru
...
Pull s390 updates from Martin Schwidefsky:
"This patch set contains the main portion of the changes for 3.18 in
regard to the s390 architecture. It is a bit bigger than usual,
mainly because of a new driver and the vector extension patches.
The interesting bits are:
- Quite a bit of work on the tracing front. Uprobes is enabled and
the ftrace code is reworked to get some of the lost performance
back if CONFIG_FTRACE is enabled.
- To improve boot time with CONFIG_DEBIG_PAGEALLOC, support for the
IPTE range facility is added.
- The rwlock code is re-factored to improve writer fairness and to be
able to use the interlocked-access instructions.
- The kernel part for the support of the vector extension is added.
- The device driver to access the CD/DVD on the HMC is added, this
will hopefully come in handy to improve the installation process.
- Add support for control-unit initiated reconfiguration.
- The crypto device driver is enhanced to enable the additional AP
domains and to allow the new crypto hardware to be used.
- Bug fixes"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (39 commits)
s390/ftrace: simplify enabling/disabling of ftrace_graph_caller
s390/ftrace: remove 31 bit ftrace support
s390/kdump: add support for vector extension
s390/disassembler: add vector instructions
s390: add support for vector extension
s390/zcrypt: Toleration of new crypto hardware
s390/idle: consolidate idle functions and definitions
s390/nohz: use a per-cpu flag for arch_needs_cpu
s390/vtime: do not reset idle data on CPU hotplug
s390/dasd: add support for control unit initiated reconfiguration
s390/dasd: fix infinite loop during format
s390/mm: make use of ipte range facility
s390/setup: correct 4-level kernel page table detection
s390/topology: call set_sched_topology early
s390/uprobes: architecture backend for uprobes
s390/uprobes: common library for kprobes and uprobes
s390/rwlock: use the interlocked-access facility 1 instructions
s390/rwlock: improve writer fairness
s390/rwlock: remove interrupt-enabling rwlock variant.
s390/mm: remove change bit override support
...
Pull x86 seccomp changes from Ingo Molnar:
"This tree includes x86 seccomp filter speedups and related preparatory
work, which touches core seccomp facilities as well.
The main idea is to split seccomp into two phases, to be able to enter
a simple fast path for syscalls with ptrace side effects.
There's no substantial user-visible (and ABI) effects expected from
this, except a change in how we emit a better audit record for
SECCOMP_RET_TRACE events"
* 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86_64, entry: Use split-phase syscall_trace_enter for 64-bit syscalls
x86_64, entry: Treat regs->ax the same in fastpath and slowpath syscalls
x86: Split syscall_trace_enter into two phases
x86, entry: Only call user_exit if TIF_NOHZ
x86, x32, audit: Fix x32's AUDIT_ARCH wrt audit
seccomp: Document two-phase seccomp and arch-provided seccomp_data
seccomp: Allow arch code to provide seccomp_data
seccomp: Refactor the filter callback and the API
seccomp,x86,arm,mips,s390: Remove nr parameter from secure_computing
Consolidate the various external const and non-const declarations of
__start___param[] and __stop___param in <linux/moduleparam.h>. This
requires making a few struct kernel_param pointers in kernel/params.c
const.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In some cases we don't want hard lockup detection enabled by default.
An example is when running as a guest. Introduce
watchdog_enable_hardlockup_detector(bool)
allowing those cases to disable hard lockup detection. This must be
executed early by the boot processor from e.g. smp_prepare_boot_cpu, in
order to allow kernel command line arguments to override it, as well as
to avoid hard lockup detection being enabled before we've had a chance
to indicate that it's unwanted. In summary,
initial boot: default=enabled
smp_prepare_boot_cpu
watchdog_enable_hardlockup_detector(false): default=disabled
cmdline has 'nmi_watchdog=1': default=enabled
The running kernel still has the ability to enable/disable at any time
with /proc/sys/kernel/nmi_watchdog us usual. However even when the
default has been overridden /proc/sys/kernel/nmi_watchdog will initially
show '1'. To truly turn it on one must disable/enable it, i.e.
echo 0 > /proc/sys/kernel/nmi_watchdog
echo 1 > /proc/sys/kernel/nmi_watchdog
This patch will be immediately useful for KVM with the next patch of this
series. Other hypervisor guest types may find it useful as well.
[akpm@linux-foundation.org: fix build]
[dzickus@redhat.com: fix compile issues on sparc]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kirill Tkhai
Peter Zijlstra
Wanpeng Li
Juri Lelli
Oleg Nesterov
Rik van Riel
Yasuaki Ishimatsu
Rafael J. Wysocki
Michal Hocko
Cong Wang
Linus Torvalds
Catalin Marinas
Prarit Bhargava
Geert Uytterhoeven
Ulrich Obergfell