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locking/static_key: Factor out the fast path of static_key_slow_dec()

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static_key_slow_dec() checks if the atomic enable count is larger
than 1, and if so there decrements it before taking the jump_label_lock.
Move this logic into a helper for reuse in rate limitted keys.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: alexei.starovoitov@gmail.com
Cc: ard.biesheuvel@linaro.org
Cc: oss-drivers@netronome.com
Cc: yamada.masahiro@socionext.com
Link: https://lkml.kernel.org/r/20190330000854.30142-3-jakub.kicinski@netronome.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Jakub Kicinski 2019-03-29 17:08:53 -07:00 committed by Ingo Molnar
parent ad282a8117
commit b92e793bbe
1 changed files with 15 additions and 8 deletions
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23
kernel/jump_label.c
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@ -202,13 +202,13 @@ void static_key_disable(struct static_key *key)
}
EXPORT_SYMBOL_GPL(static_key_disable);
static void __static_key_slow_dec_cpuslocked(struct static_key *key,
unsigned long rate_limit,
struct delayed_work *work)
static bool static_key_slow_try_dec(struct static_key *key)
{
int val;
lockdep_assert_cpus_held();
val = atomic_fetch_add_unless(&key->enabled, -1, 1);
if (val == 1)
return false;
/*
* The negative count check is valid even when a negative
@ -217,11 +217,18 @@ static void __static_key_slow_dec_cpuslocked(struct static_key *key,
* returns is unbalanced, because all other static_key_slow_inc()
* instances block while the update is in progress.
*/
val = atomic_fetch_add_unless(&key->enabled, -1, 1);
if (val != 1) {
WARN(val < 0, "jump label: negative count!\n");
WARN(val < 0, "jump label: negative count!\n");
return true;
}
static void __static_key_slow_dec_cpuslocked(struct static_key *key,
unsigned long rate_limit,
struct delayed_work *work)
{
lockdep_assert_cpus_held();
if (static_key_slow_try_dec(key))
return;
}
jump_label_lock();
if (atomic_dec_and_test(&key->enabled)) {