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author | Prateek Sood <prsood@codeaurora.org> | 2018-11-30 20:40:56 +0530 |
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committer | Ingo Molnar <mingo@kernel.org> | 2019-01-21 11:15:36 +0100 |
commit | 6dc080eeb2ba01973bfff0d79844d7a59e12542e (patch) | |
tree | 9deefb59370b698572b87e0c3467c87cd3a3f9bc /include | |
parent | d7393226d15add056285c8fc86723d54d7e0c77d (diff) | |
download | linux-stable-6dc080eeb2ba01973bfff0d79844d7a59e12542e.tar.gz linux-stable-6dc080eeb2ba01973bfff0d79844d7a59e12542e.tar.bz2 linux-stable-6dc080eeb2ba01973bfff0d79844d7a59e12542e.zip |
sched/wait: Fix rcuwait_wake_up() ordering
For some peculiar reason rcuwait_wake_up() has the right barrier in
the comment, but not in the code.
This mistake has been observed to cause a deadlock in the following
situation:
P1 P2
percpu_up_read() percpu_down_write()
rcu_sync_is_idle() // false
rcu_sync_enter()
...
__percpu_up_read()
[S] ,- __this_cpu_dec(*sem->read_count)
| smp_rmb();
[L] | task = rcu_dereference(w->task) // NULL
|
| [S] w->task = current
| smp_mb();
| [L] readers_active_check() // fail
`-> <store happens here>
Where the smp_rmb() (obviously) fails to constrain the store.
[ peterz: Added changelog. ]
Signed-off-by: Prateek Sood <prsood@codeaurora.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 8f95c90ceb54 ("sched/wait, RCU: Introduce rcuwait machinery")
Link: https://lkml.kernel.org/r/1543590656-7157-1-git-send-email-prsood@codeaurora.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include')
0 files changed, 0 insertions, 0 deletions