From: Jakub Kicinski <jakub.kicinski@netronome.com>
To: peterz@infradead.org, tglx@linutronix.de
Cc: ard.biesheuvel@linaro.org, yamada.masahiro@socionext.com,
mingo@kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, oss-drivers@netronome.com,
alexei.starovoitov@gmail.com,
Jakub Kicinski <jakub.kicinski@netronome.com>,
Simon Horman <simon.horman@netronome.com>
Subject: [PATCH 2/3] locking/static_key: factor out the fast path of static_key_slow_dec()
Date: Fri, 29 Mar 2019 17:08:53 -0700 [thread overview]
Message-ID: <20190330000854.30142-3-jakub.kicinski@netronome.com> (raw)
In-Reply-To: <20190330000854.30142-1-jakub.kicinski@netronome.com>
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>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
---
kernel/jump_label.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 73bbbaddbd9c..02c3d11264dd 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -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)) {
--
2.21.0
next prev parent reply other threads:[~2019-03-30 0:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-30 0:08 [PATCH 0/3] locking/static_key: improve rate limited labels Jakub Kicinski
2019-03-30 0:08 ` [PATCH 1/3] locking/static_key: add support for deferred static branches Jakub Kicinski
2019-04-29 6:40 ` [tip:locking/core] locking/static_key: Add " tip-bot for Jakub Kicinski
2019-03-30 0:08 ` Jakub Kicinski [this message]
2019-04-29 6:41 ` [tip:locking/core] locking/static_key: Factor out the fast path of static_key_slow_dec() tip-bot for Jakub Kicinski
2019-03-30 0:08 ` [PATCH 3/3] locking/static_key: don't take sleeping locks in __static_key_slow_dec_deferred() Jakub Kicinski
2019-04-29 6:41 ` [tip:locking/core] locking/static_key: Don't " tip-bot for Jakub Kicinski
2019-04-01 18:21 ` [PATCH 0/3] locking/static_key: improve rate limited labels Jakub Kicinski
2019-04-02 7:03 ` Peter Zijlstra
2019-04-04 10:29 ` Peter Zijlstra
2019-04-16 16:33 ` Jakub Kicinski
2019-04-16 17:38 ` Peter Zijlstra
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