Commit Graph

129 Commits

Author SHA1 Message Date
Joe Perches 7f032d6ef6 ipc: remove use of seq_printf return value
The seq_printf return value, because it's frequently misused,
will eventually be converted to void.

See: commit 1f33c41c03 ("seq_file: Rename seq_overflow() to
     seq_has_overflowed() and make public")

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-15 16:35:24 -07:00
Davidlohr Bueso 52644c9ab3 ipc,sem: use current->state helpers
Call __set_current_state() instead of assigning the new state directly.
These interfaces also aid CONFIG_DEBUG_ATOMIC_SLEEP environments, keeping
track of who changed the state.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-17 14:34:55 -08:00
Manfred Spraul 2e094abfd1 ipc/sem.c: change memory barrier in sem_lock() to smp_rmb()
When I fixed bugs in the sem_lock() logic, I was more conservative than
necessary.  Therefore it is safe to replace the smp_mb() with smp_rmb().
And: With smp_rmb(), semop() syscalls are up to 10% faster.

The race we must protect against is:

	sem->lock is free
	sma->complex_count = 0
	sma->sem_perm.lock held by thread B

thread A:

A: spin_lock(&sem->lock)

			B: sma->complex_count++; (now 1)
			B: spin_unlock(&sma->sem_perm.lock);

A: spin_is_locked(&sma->sem_perm.lock);
A: XXXXX memory barrier
A: if (sma->complex_count == 0)

Thread A must read the increased complex_count value, i.e. the read must
not be reordered with the read of sem_perm.lock done by spin_is_locked().

Since it's about ordering of reads, smp_rmb() is sufficient.

[akpm@linux-foundation.org: update sem_lock() comment, from Davidlohr]
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 12:42:52 -08:00
Manfred Spraul e8577d1f03 ipc/sem.c: fully initialize sem_array before making it visible
ipc_addid() makes a new ipc identifier visible to everyone.  New objects
start as locked, so that the caller can complete the initialization
after the call.  Within struct sem_array, at least sma->sem_base and
sma->sem_nsems are accessed without any locks, therefore this approach
doesn't work.

Thus: Move the ipc_addid() to the end of the initialization.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reported-by: Rik van Riel <riel@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-03 09:36:03 -08:00
Manfred Spraul 9b44ee2eef ipc/sem.c: add a printk_once for semctl(GETNCNT/GETZCNT)
The actual Linux implementation for semctl(GETNCNT) and semctl(GETZCNT)
always (since 0.99.10) reported a thread as sleeping on all semaphores
that are listed in the semop() call.

The documented behavior (both in the Linux man page and in the Single
Unix Specification) is that a task should be reported on exactly one
semaphore: The semaphore that caused the thread to got to sleep.

This patch adds a pr_info_once() that is triggered if a thread hits the
relevant case.

The code triggers slightly too often, otherwise it would be necessary to
replicate the old code.  As there are no known users of GETNCNT or
GETZCNT, this is done to prevent unnecessary bloat.

The task that triggered is reported with name (tsk->comm) and pid.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Acked-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:15 -07:00
Manfred Spraul b220c57aec ipc/sem.c: make semctl(,,{GETNCNT,GETZCNT}) standard compliant
SUSv4 clearly defines how semncnt and semzcnt must be calculated: A task
waits on exactly one semaphore: The semaphore from the first operation
in the sop array that cannot proceed.

The Linux implementation never followed the standard, it tried to count
all semaphores that might be the reason why a task sleeps.

This patch fixes that.

Note:
a) The implementation assumes that GETNCNT and GETZCNT are rare operations,
   therefore the code counts them only on demand.
   (If they wouldn't be rare, then the non-compliance would have
   been found earlier)

b) compared to the initial version of the patch, the BUG_ONs were removed
   and it was clarified that the new behavior conforms to SUS.

Back-compatibility concerns:

Manfred:

: - there is no application in Fedora that uses GETNCNT or GETZCNT.
:
: - application that use only single-sop semop() are also safe, the
:   difference only affects complex apps.
:
: - portable application are also safe, the new behavior is standard
:   compliant.
:
: But that's it.  The old behavior existed in Linux from 0.99.something
: until now.

Michael:

: * These operations seem to be very little used.  Grepping the public
:   source that is contained Fedora 20 source DVD, there appear to be no
:   uses.  Of course, this says nothing about uses in private /
:   non-mainstream FOSS code, but it seems likely that the same pattern
:   is followed there.
:
: * The existing behavior is hard enough to understand that I suspect
:   that no one understood it well enough to rely on it anyway
:   (especially as that behavior contradicted both man page and POSIX).
:
: So, there's a chance of breakage, but I estimate that it's minute.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:15 -07:00
Manfred Spraul ed247b7ca0 ipc/sem.c: store which operation blocks in perform_atomic_semop()
Preparation for the next patch:

In the slow-path of perform_atomic_semop(), store a pointer to the
operation that caused the operation to block.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:15 -07:00
Manfred Spraul d198cd6d6d ipc/sem.c: change perform_atomic_semop parameters
Right now, perform_atomic_semop gets the content of sem_queue as
individual fields.  Changes that, instead pass a pointer to sem_queue.

This is a preparation for the next patch: it uses sem_queue to store the
reason why a task must sleep.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:15 -07:00
Manfred Spraul 2f2ed41dca ipc/sem.c: remove code duplication
count_semzcnt and count_semncnt are more of less identical.  The patch
creates a single function that either counts the number of tasks waiting
for zero or waiting due to a decrease operation.

Compared to the initial version, the BUG_ONs were removed.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:15 -07:00
Manfred Spraul 1994862dc9 ipc/sem.c: bugfix for semctl(,,GETZCNT)
GETZCNT is supposed to return the number of threads that wait until a
semaphore value becomes 0.

The current implementation overlooks complex operations that contain
both wait-for-zero operation and operations that alter at least one
semaphore.

The patch fixes that.  It's intentionally copy&paste, this will be
cleaned up in the next patch.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:15 -07:00
Paul McQuade 46c0a8ca3e ipc, kernel: clear whitespace
trailing whitespace

Signed-off-by: Paul McQuade <paulmcquad@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:14 -07:00
Paul McQuade 7153e40273 ipc, kernel: use Linux headers
Use #include <linux/uaccess.h> instead of <asm/uaccess.h>
Use #include <linux/types.h> instead of <asm/types.h>

Signed-off-by: Paul McQuade <paulmcquad@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:14 -07:00
Mathias Krause eb66ec44f8 ipc: constify ipc_ops
There is no need to recreate the very same ipc_ops structure on every
kernel entry for msgget/semget/shmget.  Just declare it static and be
done with it.  While at it, constify it as we don't modify the structure
at runtime.

Found in the PaX patch, written by the PaX Team.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06 16:08:14 -07:00
Davidlohr Bueso 3ab08fe204 ipc: remove braces for single statements
Deal with checkpatch messages:
     WARNING: braces {} are not necessary for single statement blocks

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-27 21:02:39 -08:00
Davidlohr Bueso 8001c85810 ipc: standardize code comments
IPC commenting style is all over the place, *specially* in util.c.  This
patch orders things a bit.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-27 21:02:39 -08:00
Manfred Spraul 239521f31d ipc: whitespace cleanup
The ipc code does not adhere the typical linux coding style.
This patch fixes lots of simple whitespace errors.

- mostly autogenerated by
  scripts/checkpatch.pl -f --fix \
	--types=pointer_location,spacing,space_before_tab
- one manual fixup (keep structure members tab-aligned)
- removal of additional space_before_tab that were not found by --fix

Tested with some of my msg and sem test apps.

Andrew: Could you include it in -mm and move it towards Linus' tree?

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Suggested-by: Li Bin <huawei.libin@huawei.com>
Cc: Joe Perches <joe@perches.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-27 21:02:39 -08:00
Rafael Aquini 72a8ff2f92 ipc: change kern_ipc_perm.deleted type to bool
struct kern_ipc_perm.deleted is meant to be used as a boolean toggle, and
the changes introduced by this patch are just to make the case explicit.

Signed-off-by: Rafael Aquini <aquini@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Acked-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-27 21:02:39 -08:00
Rafael Aquini 0f3d2b0135 ipc: introduce ipc_valid_object() helper to sort out IPC_RMID races
After the locking semantics for the SysV IPC API got improved, a couple
of IPC_RMID race windows were opened because we ended up dropping the
'kern_ipc_perm.deleted' check performed way down in ipc_lock().  The
spotted races got sorted out by re-introducing the old test within the
racy critical sections.

This patch introduces ipc_valid_object() to consolidate the way we cope
with IPC_RMID races by using the same abstraction across the API
implementation.

Signed-off-by: Rafael Aquini <aquini@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-27 21:02:39 -08:00
Petr Mladek 78f5009cc3 ipc/sem.c: avoid overflow of semop undo (semadj) value
When trying to understand semop code, I found a small mistake in the check
for semadj (undo) value overflow.  The new undo value is not stored
immediately and next potential checks are done against the old value.

The failing scenario is not much practical.  One semop call has to do more
operations on the same semaphore.  Also semval and semadj must have
different values, so there has to be some operations without SEM_UNDO
flag.  For example:

	struct sembuf depositor_op[1];
	struct sembuf collector_op[2];

	depositor_op[0].sem_num = 0;
	depositor_op[0].sem_op = 20000;
	depositor_op[0].sem_flg = 0;

	collector_op[0].sem_num = 0;
	collector_op[0].sem_op = -10000;
	collector_op[0].sem_flg = SEM_UNDO;
	collector_op[1].sem_num = 0;
	collector_op[1].sem_op = -10000;
	collector_op[1].sem_flg = SEM_UNDO;

	if (semop(semid, depositor_op, 1) == -1)
		{ perror("Failed to do 1st deposit"); return 1; }

	if (semop(semid, collector_op, 2) == -1)
		{ perror("Failed to do 1st collect"); return 1; }

	if (semop(semid, depositor_op, 1) == -1)
		{ perror("Failed to do 2nd deposit"); return 1; }

	if (semop(semid, collector_op, 2) == -1)
		{ perror("Failed to do 2nd collect"); return 1; }

	return 0;

It passes without error now but the semadj value has overflown in the 2nd
collector operation.

[akpm@linux-foundation.org: restore lessened scope of local `undo']
[davidlohr@hp.com: correct header comment for perform_atomic_semop]
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Acked-by: Davidlohr Bueso <davidlohr@hp.com>
Acked-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-27 21:02:39 -08:00
Manfred Spraul 6e224f9459 ipc/sem.c: synchronize semop and semctl with IPC_RMID
After acquiring the semlock spinlock, operations must test that the
array is still valid.

 - semctl() and exit_sem() would walk stale linked lists (ugly, but
   should be ok: all lists are empty)

 - semtimedop() would sleep forever - and if woken up due to a signal -
   access memory after free.

The patch also:
 - standardizes the tests for .deleted, so that all tests in one
   function leave the function with the same approach.
 - unconditionally tests for .deleted immediately after every call to
   sem_lock - even it it means that for semctl(GETALL), .deleted will be
   tested twice.

Both changes make the review simpler: After every sem_lock, there must
be a test of .deleted, followed by a goto to the cleanup code (if the
function uses "goto cleanup").

The only exception is semctl_down(): If sem_ids().rwsem is locked, then
the presence in ids->ipcs_idr is equivalent to !.deleted, thus no
additional test is required.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Mike Galbraith <efault@gmx.de>
Acked-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-10-16 21:35:52 -07:00
Manfred Spraul 0e8c665699 ipc/sem.c: update sem_otime for all operations
In commit 0a2b9d4c79 ("ipc/sem.c: move wake_up_process out of the
spinlock section"), the update of semaphore's sem_otime(last semop time)
was moved to one central position (do_smart_update).

But since do_smart_update() is only called for operations that modify
the array, this means that wait-for-zero semops do not update sem_otime
anymore.

The fix is simple:
Non-alter operations must update sem_otime.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reported-by: Jia He <jiakernel@gmail.com>
Tested-by: Jia He <jiakernel@gmail.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-30 14:31:03 -07:00
Manfred Spraul d8c633766a ipc/sem.c: synchronize the proc interface
The proc interface is not aware of sem_lock(), it instead calls
ipc_lock_object() directly.  This means that simple semop() operations
can run in parallel with the proc interface.  Right now, this is
uncritical, because the implementation doesn't do anything that requires
a proper synchronization.

But it is dangerous and therefore should be fixed.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-30 14:31:01 -07:00
Manfred Spraul 6d07b68ce1 ipc/sem.c: optimize sem_lock()
Operations that need access to the whole array must guarantee that there
are no simple operations ongoing.  Right now this is achieved by
spin_unlock_wait(sem->lock) on all semaphores.

If complex_count is nonzero, then this spin_unlock_wait() is not
necessary, because it was already performed in the past by the thread
that increased complex_count and even though sem_perm.lock was dropped
inbetween, no simple operation could have started, because simple
operations cannot start when complex_count is non-zero.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-30 14:31:01 -07:00
Manfred Spraul 5e9d527591 ipc/sem.c: fix race in sem_lock()
The exclusion of complex operations in sem_lock() is insufficient: after
acquiring the per-semaphore lock, a simple op must first check that
sem_perm.lock is not locked and only after that test check
complex_count.  The current code does it the other way around - and that
creates a race.  Details are below.

The patch is a complete rewrite of sem_lock(), based in part on the code
from Mike Galbraith.  It removes all gotos and all loops and thus the
risk of livelocks.

I have tested the patch (together with the next one) on my i3 laptop and
it didn't cause any problems.

The bug is probably also present in 3.10 and 3.11, but for these kernels
it might be simpler just to move the test of sma->complex_count after
the spin_is_locked() test.

Details of the bug:

Assume:
 - sma->complex_count = 0.
 - Thread 1: semtimedop(complex op that must sleep)
 - Thread 2: semtimedop(simple op).

Pseudo-Trace:

Thread 1: sem_lock(): acquire sem_perm.lock
Thread 1: sem_lock(): check for ongoing simple ops
			Nothing ongoing, thread 2 is still before sem_lock().
Thread 1: try_atomic_semop()
	<<< preempted.

Thread 2: sem_lock():
        static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
                                      int nsops)
        {
                int locknum;
         again:
                if (nsops == 1 && !sma->complex_count) {
                        struct sem *sem = sma->sem_base + sops->sem_num;

                        /* Lock just the semaphore we are interested in. */
                        spin_lock(&sem->lock);

                        /*
                         * If sma->complex_count was set while we were spinning,
                         * we may need to look at things we did not lock here.
                         */
                        if (unlikely(sma->complex_count)) {
                                spin_unlock(&sem->lock);
                                goto lock_array;
                        }
        <<<<<<<<<
	<<< complex_count is still 0.
	<<<
        <<< Here it is preempted
        <<<<<<<<<

Thread 1: try_atomic_semop() returns, notices that it must sleep.
Thread 1: increases sma->complex_count.
Thread 1: drops sem_perm.lock
Thread 2:
                /*
                 * Another process is holding the global lock on the
                 * sem_array; we cannot enter our critical section,
                 * but have to wait for the global lock to be released.
                 */
                if (unlikely(spin_is_locked(&sma->sem_perm.lock))) {
                        spin_unlock(&sem->lock);
                        spin_unlock_wait(&sma->sem_perm.lock);
                        goto again;
                }
	<<< sem_perm.lock already dropped, thus no "goto again;"

                locknum = sops->sem_num;

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: <stable@vger.kernel.org>	[3.10+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-30 14:31:01 -07:00
Davidlohr Bueso 53dad6d3a8 ipc: fix race with LSMs
Currently, IPC mechanisms do security and auditing related checks under
RCU.  However, since security modules can free the security structure,
for example, through selinux_[sem,msg_queue,shm]_free_security(), we can
race if the structure is freed before other tasks are done with it,
creating a use-after-free condition.  Manfred illustrates this nicely,
for instance with shared mem and selinux:

 -> do_shmat calls rcu_read_lock()
 -> do_shmat calls shm_object_check().
     Checks that the object is still valid - but doesn't acquire any locks.
     Then it returns.
 -> do_shmat calls security_shm_shmat (e.g. selinux_shm_shmat)
 -> selinux_shm_shmat calls ipc_has_perm()
 -> ipc_has_perm accesses ipc_perms->security

shm_close()
 -> shm_close acquires rw_mutex & shm_lock
 -> shm_close calls shm_destroy
 -> shm_destroy calls security_shm_free (e.g. selinux_shm_free_security)
 -> selinux_shm_free_security calls ipc_free_security(&shp->shm_perm)
 -> ipc_free_security calls kfree(ipc_perms->security)

This patch delays the freeing of the security structures after all RCU
readers are done.  Furthermore it aligns the security life cycle with
that of the rest of IPC - freeing them based on the reference counter.
For situations where we need not free security, the current behavior is
kept.  Linus states:

 "... the old behavior was suspect for another reason too: having the
  security blob go away from under a user sounds like it could cause
  various other problems anyway, so I think the old code was at least
  _prone_ to bugs even if it didn't have catastrophic behavior."

I have tested this patch with IPC testcases from LTP on both my
quad-core laptop and on a 64 core NUMA server.  In both cases selinux is
enabled, and tests pass for both voluntary and forced preemption models.
While the mentioned races are theoretical (at least no one as reported
them), I wanted to make sure that this new logic doesn't break anything
we weren't aware of.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Acked-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-24 09:36:53 -07:00
Davidlohr Bueso d9a605e40b ipc: rename ids->rw_mutex
Since in some situations the lock can be shared for readers, we shouldn't
be calling it a mutex, rename it to rwsem.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-11 15:59:42 -07:00
Manfred Spraul 758a6ba39e ipc/sem.c: rename try_atomic_semop() to perform_atomic_semop(), docu update
Cleanup: Some minor points that I noticed while writing the previous
patches

1) The name try_atomic_semop() is misleading: The function performs the
   operation (if it is possible).

2) Some documentation updates.

No real code change, a rename and documentation changes.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:28 -07:00
Manfred Spraul d12e1e50e4 ipc/sem.c: replace shared sem_otime with per-semaphore value
sem_otime contains the time of the last semaphore operation that
completed successfully.  Every operation updates this value, thus access
from multiple cpus can cause thrashing.

Therefore the patch replaces the variable with a per-semaphore variable.
The per-array sem_otime is only calculated when required.

No performance improvement on a single-socket i3 - only important for
larger systems.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:28 -07:00
Manfred Spraul f269f40ad5 ipc/sem.c: always use only one queue for alter operations
There are two places that can contain alter operations:
 - the global queue: sma->pending_alter
 - the per-semaphore queues: sma->sem_base[].pending_alter.

Since one of the queues must be processed first, this causes an odd
priorization of the wakeups: complex operations have priority over
simple ops.

The patch restores the behavior of linux <=3.0.9: The longest waiting
operation has the highest priority.

This is done by using only one queue:
 - if there are complex ops, then sma->pending_alter is used.
 - otherwise, the per-semaphore queues are used.

As a side effect, do_smart_update_queue() becomes much simpler: no more
goto logic.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:28 -07:00
Manfred Spraul 1a82e9e1d0 ipc/sem: separate wait-for-zero and alter tasks into seperate queues
Introduce separate queues for operations that do not modify the
semaphore values.  Advantages:

 - Simpler logic in check_restart().
 - Faster update_queue(): Right now, all wait-for-zero operations are
   always tested, even if the semaphore value is not 0.
 - wait-for-zero gets again priority, as in linux <=3.0.9

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:28 -07:00
Manfred Spraul f5c936c0f2 ipc/sem.c: cacheline align the semaphore structures
As now each semaphore has its own spinlock and parallel operations are
possible, give each semaphore its own cacheline.

On a i3 laptop, this gives up to 28% better performance:

  #semscale 10 | grep "interleave 2"
  - before:
  Cpus 1, interleave 2 delay 0: 36109234 in 10 secs
  Cpus 2, interleave 2 delay 0: 55276317 in 10 secs
  Cpus 3, interleave 2 delay 0: 62411025 in 10 secs
  Cpus 4, interleave 2 delay 0: 81963928 in 10 secs

  -after:
  Cpus 1, interleave 2 delay 0: 35527306 in 10 secs
  Cpus 2, interleave 2 delay 0: 70922909 in 10 secs <<< + 28%
  Cpus 3, interleave 2 delay 0: 80518538 in 10 secs
  Cpus 4, interleave 2 delay 0: 89115148 in 10 secs <<< + 8.7%

i3, with 2 cores and with hyperthreading enabled.  Interleave 2 in order
use first the full cores.  HT partially hides the delay from cacheline
trashing, thus the improvement is "only" 8.7% if 4 threads are running.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:28 -07:00
Davidlohr Bueso 9ad66ae65f ipc: remove unused functions
We can now drop the msg_lock and msg_lock_check functions along with a
bogus comment introduced previously in semctl_down.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:27 -07:00
Davidlohr Bueso 7b4cc5d841 ipc: move locking out of ipcctl_pre_down_nolock
This function currently acquires both the rw_mutex and the rcu lock on
successful lookups, leaving the callers to explicitly unlock them,
creating another two level locking situation.

Make the callers (including those that still use ipcctl_pre_down())
explicitly lock and unlock the rwsem and rcu lock.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:27 -07:00
Davidlohr Bueso cf9d5d78d0 ipc: close open coded spin lock calls
Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09 10:33:27 -07:00
Manfred Spraul ab465df9dd ipc/sem.c: Fix missing wakeups in do_smart_update_queue()
do_smart_update_queue() is called when an operation (semop,
semctl(SETVAL), semctl(SETALL), ...) modified the array.  It must check
which of the sleeping tasks can proceed.

do_smart_update_queue() missed a few wakeups:
 - if a sleeping complex op was completed, then all per-semaphore queues
   must be scanned - not only those that were modified by *sops
 - if a sleeping simple op proceeded, then the global queue must be
   scanned again

And:
 - the test for "|sops == NULL) before scanning the global queue is not
   required: If the global queue is empty, then it doesn't need to be
   scanned - regardless of the reason for calling do_smart_update_queue()

The patch is not optimized, i.e.  even completing a wait-for-zero
operation causes a rescan.  This is done to keep the patch as simple as
possible.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-26 15:14:51 -07:00
Rik van Riel de2657f94a ipc,sem: fix semctl(..., GETNCNT)
The semctl GETNCNT returns the number of semops waiting for the
specified semaphore to become nonzero.  After commit 9f1bc2c902
("ipc,sem: have only one list in struct sem_queue"), the semops waiting
on just one semaphore are waiting on that semaphore's list.

In order to return the correct count, we have to walk that list too, in
addition to the sem_array's list for complex operations.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-09 14:17:47 -07:00
Rik van Riel ebc2e5e6a4 ipc,sem: fix semctl(..., GETZCNT)
The semctl GETZCNT returns the number of semops waiting for the
specified semaphore to become zero.  After commit 9f1bc2c902
("ipc,sem: have only one list in struct sem_queue"), the semops waiting
on just one semaphore are waiting on that semaphore's list.

In order to return the correct count, we have to walk that list too, in
addition to the sem_array's list for complex operations.

This bug broke dbench; it works again with this patch applied.

Signed-off-by: Rik van Riel <riel@redhat.com>
Reported-by: Kent Overstreet <koverstreet@google.com>
Tested-by: Kent Overstreet <koverstreet@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-09 14:17:47 -07:00
Linus Torvalds 941b0304a7 ipc: simplify rcu_read_lock() in semctl_nolock()
This trivially combines two rcu_read_lock() calls in both sides of a
if-statement into one single one in front of the if-statement.

Split out as an independent cleanup from the previous commit.

Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-04 17:24:59 -07:00
Linus Torvalds c728b9c87b ipc: simplify semtimedop/semctl_main() common error path handling
With various straight RCU lock/unlock movements, one common exit path
pattern had become

	rcu_read_unlock();
	goto out_wakeup;

and in fact there were no cases where we wanted to exit to out_wakeup
_without_ releasing the RCU read lock.

So replace that pattern with "goto out_rcu_wakeup", and remove the old
out_wakeup.

Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-04 17:21:58 -07:00
Linus Torvalds 321310ced2 ipc: move sem_obtain_lock() rcu locking into the only caller
sem_obtain_lock() was another of those functions that returned with the
RCU lock held for reading in the success case.  Move the RCU locking to
the caller (semtimedop()), making it more obvious.  We already did RCU
locking elsewhere in that function.

Side note: why does semtimedop() re-do the semphore lookup after the
sleep, rather than just getting a reference to the semaphore it already
looked up originally?

Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-04 17:20:14 -07:00
Linus Torvalds fbfd1d2862 ipc: fix double sem unlock in semctl error path
Fix another ipc locking buglet introduced by the scalability patches:
when semctl_down() was changed to delay the semaphore locking, one error
path for security_sem_semctl() went through the semaphore unlock logic
even though the semaphore had never been locked.

Introduced by commit 16df3674ef ("ipc,sem: do not hold ipc lock more
than necessary")

Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-04 17:19:59 -07:00
Linus Torvalds 4091fd942e ipc: move the rcu_read_lock() from sem_lock_and_putref() into callers
This is another ipc semaphore locking cleanup, trying to make the
locking more straightforward.  We move the rcu read locking into the
callers of sem_lock_and_putref(), which in general means that we now
mostly do the rcu_read_lock() and rcu_read_unlock() in the same
function.

Mostly.  We still have the ipc_addid/newary/freeary mess, and things
like ipcctl_pre_down_nolock().

Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-04 17:19:39 -07:00
Linus Torvalds 73b29505c3 ipc: sem_putref() does not need the semaphore lock any more
ipc_rcu_putref() uses atomics for the refcount, and the games to lock
and unlock the semaphore just to try to keep the reference counting
working are no longer useful.

Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-04 11:24:21 -07:00
Linus Torvalds 6d49dab8ae ipc: move rcu_read_unlock() out of sem_unlock() and into callers
The IPC locking is a mess, and sem_unlock() unlocks not only the
semaphore spinlock, it also drops the rcu read lock.  Unlike sem_lock(),
which just gets the spin-lock, and expects the caller to get the rcu
read lock.

This all makes things very hard to follow, and it's very confusing when
you take the rcu read lock in one function, and then release it in
another.  And it has caused actual bugs: the sem_obtain_lock() function
ended up dropping the RCU read lock twice in one error path, because it
first did the sem_unlock(), and then did a rcu_read_unlock() to match
the rcu_read_lock() it had done.

This is just a totally mindless "remove rcu_read_unlock() from
sem_unlock() and add it immediately after each caller" (except for the
aforementioned bug where we did too many rcu_read_unlock(), and in
find_alloc_undo() where we just got the rcu_read_lock() to correct for
the fact that sem_unlock would immediately drop it again).

We can (and should) clean things up further, but this fixes the bug with
the minimal amount of subtlety.

Reviewed-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-04 11:24:00 -07:00
Al Viro ce857229e0 ipc: fix GETALL/IPC_RM race for sysv semaphores
We can step on WARN_ON_ONCE() in sem_getref() if a semaphore is removed
just as we are about to call sem_getref() from semctl_main(); results
are not pretty.

We should fail with -EIDRM, same as if IPC_RM happened while we'd been
doing allocation there.  This also expands sem_getref() at its only
callsite (and fixed there), while sem_getref_and_unlock() is simply
killed off - it has no callers at all.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-02 19:51:31 -07:00
Rik van Riel 6062a8dc05 ipc,sem: fine grained locking for semtimedop
Introduce finer grained locking for semtimedop, to handle the common case
of a program wanting to manipulate one semaphore from an array with
multiple semaphores.

If the call is a semop manipulating just one semaphore in an array with
multiple semaphores, only take the lock for that semaphore itself.

If the call needs to manipulate multiple semaphores, or another caller is
in a transaction that manipulates multiple semaphores, the sem_array lock
is taken, as well as all the locks for the individual semaphores.

On a 24 CPU system, performance numbers with the semop-multi
test with N threads and N semaphores, look like this:

	vanilla		Davidlohr's	Davidlohr's +	Davidlohr's +
threads			patches		rwlock patches	v3 patches
10	610652		726325		1783589		2142206
20	341570		365699		1520453		1977878
30	288102		307037		1498167		2037995
40	290714		305955		1612665		2256484
50	288620		312890		1733453		2650292
60	289987		306043		1649360		2388008
70	291298		306347		1723167		2717486
80	290948		305662		1729545		2763582
90	290996		306680		1736021		2757524
100	292243		306700		1773700		3059159

[davidlohr.bueso@hp.com: do not call sem_lock when bogus sma]
[davidlohr.bueso@hp.com: make refcounter atomic]
Signed-off-by: Rik van Riel <riel@redhat.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Cc: Jason Low <jason.low2@hp.com>
Reviewed-by: Michel Lespinasse <walken@google.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Tested-by: Emmanuel Benisty <benisty.e@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-01 08:12:58 -07:00
Rik van Riel 9f1bc2c902 ipc,sem: have only one list in struct sem_queue
Having only one list in struct sem_queue, and only queueing simple
semaphore operations on the list for the semaphore involved, allows us to
introduce finer grained locking for semtimedop.

Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Cc: Emmanuel Benisty <benisty.e@gmail.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-01 08:12:58 -07:00
Rik van Riel c460b662d5 ipc,sem: open code and rename sem_lock
Rename sem_lock() to sem_obtain_lock(), so we can introduce a sem_lock()
later that only locks the sem_array and does nothing else.

Open code the locking from ipc_lock() in sem_obtain_lock() so we can
introduce finer grained locking for the sem_array in the next patch.

[akpm@linux-foundation.org: propagate the ipc_obtain_object() errno out of sem_obtain_lock()]
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Cc: Emmanuel Benisty <benisty.e@gmail.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-01 08:12:58 -07:00
Davidlohr Bueso 16df3674ef ipc,sem: do not hold ipc lock more than necessary
Instead of holding the ipc lock for permissions and security checks, among
others, only acquire it when necessary.

Some numbers....

1) With Rik's semop-multi.c microbenchmark we can see the following
   results:

Baseline (3.9-rc1):
cpus 4, threads: 256, semaphores: 128, test duration: 30 secs
total operations: 151452270, ops/sec 5048409

+  59.40%            a.out  [kernel.kallsyms]  [k] _raw_spin_lock
+   6.14%            a.out  [kernel.kallsyms]  [k] sys_semtimedop
+   3.84%            a.out  [kernel.kallsyms]  [k] avc_has_perm_flags
+   3.64%            a.out  [kernel.kallsyms]  [k] __audit_syscall_exit
+   2.06%            a.out  [kernel.kallsyms]  [k] copy_user_enhanced_fast_string
+   1.86%            a.out  [kernel.kallsyms]  [k] ipc_lock

With this patchset:
cpus 4, threads: 256, semaphores: 128, test duration: 30 secs
total operations: 273156400, ops/sec 9105213

+  18.54%            a.out  [kernel.kallsyms]  [k] _raw_spin_lock
+  11.72%            a.out  [kernel.kallsyms]  [k] sys_semtimedop
+   7.70%            a.out  [kernel.kallsyms]  [k] ipc_has_perm.isra.21
+   6.58%            a.out  [kernel.kallsyms]  [k] avc_has_perm_flags
+   6.54%            a.out  [kernel.kallsyms]  [k] __audit_syscall_exit
+   4.71%            a.out  [kernel.kallsyms]  [k] ipc_obtain_object_check

2) While on an Oracle swingbench DSS (data mining) workload the
   improvements are not as exciting as with Rik's benchmark, we can see
   some positive numbers.  For an 8 socket machine the following are the
   percentages of %sys time incurred in the ipc lock:

Baseline (3.9-rc1):
100 swingbench users: 8,74%
400 swingbench users: 21,86%
800 swingbench users: 84,35%

With this patchset:
100 swingbench users: 8,11%
400 swingbench users: 19,93%
800 swingbench users: 77,69%

[riel@redhat.com: fix two locking bugs]
[sasha.levin@oracle.com: prevent releasing RCU read lock twice in semctl_main]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Chegu Vinod <chegu_vinod@hp.com>
Acked-by: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Emmanuel Benisty <benisty.e@gmail.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-01 08:12:58 -07:00
Al Viro e1fd1f490f get rid of union semop in sys_semctl(2) arguments
just have the bugger take unsigned long and deal with SETVAL
case (when we use an int member in the union) explicitly.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-03-05 15:14:16 -05:00