diff options
| author | Peter Zijlstra | 2020-07-02 14:52:11 +0200 |
|---|---|---|
| committer | Peter Zijlstra | 2020-07-22 10:22:03 +0200 |
| commit | 58877d347b58c9e971112df5eb311c13bb0acb28 (patch) | |
| tree | 774a99deb14c018897132146841f280b17ee88ae /include | |
| parent | 015dc08918785201199ed3450c22bb8939f09dfe (diff) | |
sched: Better document ttwu()
Dave hit the problem fixed by commit:
b6e13e85829f ("sched/core: Fix ttwu() race")
and failed to understand much of the code involved. Per his request a
few comments to (hopefully) clarify things.
Requested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200702125211.GQ4800@hirez.programming.kicks-ass.net
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/sched.h | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 12b10ce51a08..5033813fecd5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -154,24 +154,24 @@ struct task_group; * * for (;;) { * set_current_state(TASK_UNINTERRUPTIBLE); - * if (!need_sleep) - * break; + * if (CONDITION) + * break; * * schedule(); * } * __set_current_state(TASK_RUNNING); * * If the caller does not need such serialisation (because, for instance, the - * condition test and condition change and wakeup are under the same lock) then + * CONDITION test and condition change and wakeup are under the same lock) then * use __set_current_state(). * * The above is typically ordered against the wakeup, which does: * - * need_sleep = false; + * CONDITION = 1; * wake_up_state(p, TASK_UNINTERRUPTIBLE); * - * where wake_up_state() executes a full memory barrier before accessing the - * task state. + * where wake_up_state()/try_to_wake_up() executes a full memory barrier before + * accessing p->state. * * Wakeup will do: if (@state & p->state) p->state = TASK_RUNNING, that is, * once it observes the TASK_UNINTERRUPTIBLE store the waking CPU can issue a |