linux/kernel/sched
Juri Lelli e117cb52bd sched/deadline: Fix switched_from_dl() warning
Mark noticed that syzkaller is able to reliably trigger the following warning:

  dl_rq->running_bw > dl_rq->this_bw
  WARNING: CPU: 1 PID: 153 at kernel/sched/deadline.c:124 switched_from_dl+0x454/0x608
  Kernel panic - not syncing: panic_on_warn set ...

  CPU: 1 PID: 153 Comm: syz-executor253 Not tainted 4.18.0-rc3+ #29
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   dump_backtrace+0x0/0x458
   show_stack+0x20/0x30
   dump_stack+0x180/0x250
   panic+0x2dc/0x4ec
   __warn_printk+0x0/0x150
   report_bug+0x228/0x2d8
   bug_handler+0xa0/0x1a0
   brk_handler+0x2f0/0x568
   do_debug_exception+0x1bc/0x5d0
   el1_dbg+0x18/0x78
   switched_from_dl+0x454/0x608
   __sched_setscheduler+0x8cc/0x2018
   sys_sched_setattr+0x340/0x758
   el0_svc_naked+0x30/0x34

syzkaller reproducer runs a bunch of threads that constantly switch
between DEADLINE and NORMAL classes while interacting through futexes.

The splat above is caused by the fact that if a DEADLINE task is setattr
back to NORMAL while in non_contending state (blocked on a futex -
inactive timer armed), its contribution to running_bw is not removed
before sub_rq_bw() gets called (!task_on_rq_queued() branch) and the
latter sees running_bw > this_bw.

Fix it by removing a task contribution from running_bw if the task is
not queued and in non_contending state while switched to a different
class.

Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Reviewed-by: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: claudio@evidence.eu.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/20180711072948.27061-1-juri.lelli@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-07-15 23:47:33 +02:00
..
Makefile sched/idle: Merge kernel/sched/idle.c and kernel/sched/idle_task.c 2018-03-04 12:39:33 +01:00
autogroup.c sched/autogroup: Fix possible Spectre-v1 indexing for sched_prio_to_weight[] 2018-05-05 08:34:42 +02:00
autogroup.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
clock.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
completion.c sched/completions: Use bool in try_wait_for_completion() 2018-03-09 08:00:18 +01:00
core.c kthread, sched/core: Fix kthread_parkme() (again...) 2018-07-03 09:17:30 +02:00
cpuacct.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpudeadline.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpudeadline.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpufreq.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpufreq_schedutil.c sched/rt: Fix call to cpufreq_update_util() 2018-07-03 09:17:28 +02:00
cpupri.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpupri.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cputime.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
deadline.c sched/deadline: Fix switched_from_dl() warning 2018-07-15 23:47:33 +02:00
debug.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
fair.c sched/util_est: Fix util_est_dequeue() for throttled cfs_rq 2018-07-03 09:17:30 +02:00
features.h sched/fair: Update util_est only on util_avg updates 2018-03-20 08:11:09 +01:00
idle.c sched: idle: Select idle state before stopping the tick 2018-04-09 11:54:07 +02:00
isolation.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
loadavg.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
membarrier.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
rt.c sched/rt: Fix call to cpufreq_update_util() 2018-07-03 09:17:28 +02:00
sched-pelt.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sched.h sched/fair: Fix bandwidth timer clock drift condition 2018-07-03 09:17:29 +02:00
stats.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
stats.h sched: Clean up and harmonize the coding style of the scheduler code base 2018-03-03 15:50:21 +01:00
stop_task.c sched: Clean up and harmonize the coding style of the scheduler code base 2018-03-03 15:50:21 +01:00
swait.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
topology.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
wait.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
wait_bit.c sched/wait: Improve __var_waitqueue() code generation 2018-03-20 08:23:25 +01:00