NeilBrown ac9a6b8638 sched: Add test_and_clear_wake_up_bit() and atomic_dec_and_wake_up() ...

[ Upstream commit 52d633def5 ]

There are common patterns in the kernel of using test_and_clear_bit()
before wake_up_bit(), and atomic_dec_and_test() before wake_up_var().

These combinations don't need extra barriers but sometimes include them
unnecessarily.

To help avoid the unnecessary barriers and to help discourage the
general use of wake_up_bit/var (which is a fragile interface) introduce
two combined functions which implement these patterns.

Also add store_release_wake_up() which supports the task of simply
setting a non-atomic variable and sending a wakeup.  This pattern
requires barriers which are often omitted.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240925053405.3960701-5-neilb@suse.de
Stable-dep-of: 1db3a48e83 ("NFS: Fix wakeup of __nfs_lookup_revalidate() in unblock_revalidate()")
Signed-off-by: Sasha Levin <sashal@kernel.org>

2025-08-15 12:14:04 +02:00

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