diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2016-12-21 11:05:02 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-01-14 13:30:01 +0300 |
| commit | da9647e076d440190fff4b4ee0f4b829dd6e8c4f (patch) | |
| tree | 7bedc99c5a41500084b0ef26673cb64ab751de0e /kernel/sched | |
| parent | 59f8c2989283bbd3df9fcfb22494d84f4852e536 (diff) | |
| download | linux-da9647e076d440190fff4b4ee0f4b829dd6e8c4f.tar.xz | |
sched/completions: Fix complete_all() semantics
Documentation/scheduler/completion.txt says this about complete_all():
"calls complete_all() to signal all current and future waiters."
Which doesn't strictly match the current semantics. Currently
complete_all() is equivalent to UINT_MAX/2 complete() invocations,
which is distinctly less than 'all current and future waiters'
(enumerable vs innumerable), although it has worked in practice.
However, Dmitry had a weird case where it might matter, so change
completions to use saturation semantics for complete()/complete_all().
Once done hits UINT_MAX (and complete_all() sets it there) it will
never again be decremented.
Requested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: der.herr@hofr.at
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/completion.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c index 8d0f35debf35..f063a25d4449 100644 --- a/kernel/sched/completion.c +++ b/kernel/sched/completion.c @@ -31,7 +31,8 @@ void complete(struct completion *x) unsigned long flags; spin_lock_irqsave(&x->wait.lock, flags); - x->done++; + if (x->done != UINT_MAX) + x->done++; __wake_up_locked(&x->wait, TASK_NORMAL, 1); spin_unlock_irqrestore(&x->wait.lock, flags); } @@ -51,7 +52,7 @@ void complete_all(struct completion *x) unsigned long flags; spin_lock_irqsave(&x->wait.lock, flags); - x->done += UINT_MAX/2; + x->done = UINT_MAX; __wake_up_locked(&x->wait, TASK_NORMAL, 0); spin_unlock_irqrestore(&x->wait.lock, flags); } @@ -79,7 +80,8 @@ do_wait_for_common(struct completion *x, if (!x->done) return timeout; } - x->done--; + if (x->done != UINT_MAX) + x->done--; return timeout ?: 1; } @@ -280,7 +282,7 @@ bool try_wait_for_completion(struct completion *x) spin_lock_irqsave(&x->wait.lock, flags); if (!x->done) ret = 0; - else + else if (x->done != UINT_MAX) x->done--; spin_unlock_irqrestore(&x->wait.lock, flags); return ret; |