From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, linux-mm@kvack.org, Shaohua Li <shli@kernel.org>, linux-raid@vger.kernel.org, Anna-Maria Gleixner <anna-maria@linutronix.de>, Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, linux-alpha@vger.kernel.org Subject: [PATCH 1/5 v2] spinlock: atomic_dec_and_lock: Add an irqsave variant Date: Mon, 4 Jun 2018 12:25:59 +0200 [thread overview] Message-ID: <20180604102559.2ynbassthjzva62l@linutronix.de> (raw) In-Reply-To: <20180504154533.8833-2-bigeasy@linutronix.de> There are in-tree users of atomic_dec_and_lock() which must acquire the spin lock with interrupts disabled. To workaround the lack of an irqsave variant of atomic_dec_and_lock() they use local_irq_save() at the call site. This causes extra code and creates in some places unneeded long interrupt disabled times. These places need also extra treatment for PREEMPT_RT due to the disconnect of the irq disabling and the lock function. Implement the missing irqsave variant of the function. Add a stub for Alpha which should work without the assmebly optimisation for the fastpath. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> [not the Alpha bits] Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Matt Turner <mattst88@gmail.com> Cc: linux-alpha@vger.kernel.org Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> [bigeasy: adding Alpha bits] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- v1…v2: Add Alpha bits (kbuild reported build failure on Alpha) arch/alpha/lib/dec_and_lock.c | 16 ++++++++++++++++ include/linux/spinlock.h | 5 +++++ lib/dec_and_lock.c | 16 ++++++++++++++++ 3 files changed, 37 insertions(+) diff --git a/arch/alpha/lib/dec_and_lock.c b/arch/alpha/lib/dec_and_lock.c index a117707f57fe..069fef7372dc 100644 --- a/arch/alpha/lib/dec_and_lock.c +++ b/arch/alpha/lib/dec_and_lock.c @@ -42,3 +42,19 @@ static int __used atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock) return 0; } EXPORT_SYMBOL(_atomic_dec_and_lock); + +int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flags) +{ + /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */ + if (atomic_add_unless(atomic, -1, 1)) + return 0; + + /* Otherwise do it the slow way */ + spin_lock_irqsave(lock, *flags); + if (atomic_dec_and_test(atomic)) + return 1; + spin_unlock_irqrestore(lock, *flags); + return 0; +} +EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave); diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 4894d322d258..803536c992f5 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -409,6 +409,11 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock); #define atomic_dec_and_lock(atomic, lock) \ __cond_lock(lock, _atomic_dec_and_lock(atomic, lock)) +extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flags); +#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \ + __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags))) + int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask, size_t max_size, unsigned int cpu_mult, gfp_t gfp); diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c index 347fa7ac2e8a..9555b68bb774 100644 --- a/lib/dec_and_lock.c +++ b/lib/dec_and_lock.c @@ -33,3 +33,19 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) } EXPORT_SYMBOL(_atomic_dec_and_lock); + +int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flags) +{ + /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */ + if (atomic_add_unless(atomic, -1, 1)) + return 0; + + /* Otherwise do it the slow way */ + spin_lock_irqsave(lock, *flags); + if (atomic_dec_and_test(atomic)) + return 1; + spin_unlock_irqrestore(lock, *flags); + return 0; +} +EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave); -- 2.17.1
WARNING: multiple messages have this Message-ID (diff)
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, linux-mm@kvack.org, Shaohua Li <shli@kernel.org>, linux-raid@vger.kernel.org, Anna-Maria Gleixner <anna-maria@linutronix.de>, Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, linux-alpha@vger.kernel.org Subject: [PATCH 1/5 v2] spinlock: atomic_dec_and_lock: Add an irqsave variant Date: Mon, 4 Jun 2018 12:25:59 +0200 [thread overview] Message-ID: <20180604102559.2ynbassthjzva62l@linutronix.de> (raw) In-Reply-To: <20180504154533.8833-2-bigeasy@linutronix.de> There are in-tree users of atomic_dec_and_lock() which must acquire the spin lock with interrupts disabled. To workaround the lack of an irqsave variant of atomic_dec_and_lock() they use local_irq_save() at the call site. This causes extra code and creates in some places unneeded long interrupt disabled times. These places need also extra treatment for PREEMPT_RT due to the disconnect of the irq disabling and the lock function. Implement the missing irqsave variant of the function. Add a stub for Alpha which should work without the assmebly optimisation for the fastpath. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> [not the Alpha bits] Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Matt Turner <mattst88@gmail.com> Cc: linux-alpha@vger.kernel.org Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> [bigeasy: adding Alpha bits] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- v1…v2: Add Alpha bits (kbuild reported build failure on Alpha) arch/alpha/lib/dec_and_lock.c | 16 ++++++++++++++++ include/linux/spinlock.h | 5 +++++ lib/dec_and_lock.c | 16 ++++++++++++++++ 3 files changed, 37 insertions(+) diff --git a/arch/alpha/lib/dec_and_lock.c b/arch/alpha/lib/dec_and_lock.c index a117707f57fe..069fef7372dc 100644 --- a/arch/alpha/lib/dec_and_lock.c +++ b/arch/alpha/lib/dec_and_lock.c @@ -42,3 +42,19 @@ static int __used atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock) return 0; } EXPORT_SYMBOL(_atomic_dec_and_lock); + +int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flags) +{ + /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */ + if (atomic_add_unless(atomic, -1, 1)) + return 0; + + /* Otherwise do it the slow way */ + spin_lock_irqsave(lock, *flags); + if (atomic_dec_and_test(atomic)) + return 1; + spin_unlock_irqrestore(lock, *flags); + return 0; +} +EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave); diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 4894d322d258..803536c992f5 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -409,6 +409,11 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock); #define atomic_dec_and_lock(atomic, lock) \ __cond_lock(lock, _atomic_dec_and_lock(atomic, lock)) +extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flags); +#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \ + __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags))) + int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask, size_t max_size, unsigned int cpu_mult, gfp_t gfp); diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c index 347fa7ac2e8a..9555b68bb774 100644 --- a/lib/dec_and_lock.c +++ b/lib/dec_and_lock.c @@ -33,3 +33,19 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) } EXPORT_SYMBOL(_atomic_dec_and_lock); + +int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, + unsigned long *flags) +{ + /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */ + if (atomic_add_unless(atomic, -1, 1)) + return 0; + + /* Otherwise do it the slow way */ + spin_lock_irqsave(lock, *flags); + if (atomic_dec_and_test(atomic)) + return 1; + spin_unlock_irqrestore(lock, *flags); + return 0; +} +EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave); -- 2.17.1
next prev parent reply other threads:[~2018-06-04 10:25 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-04 15:45 Introduce atomic_dec_and_lock_irqsave() Sebastian Andrzej Siewior 2018-05-04 15:45 ` [PATCH 1/5] spinlock: atomic_dec_and_lock: Add an irqsave variant Sebastian Andrzej Siewior 2018-06-04 10:25 ` Sebastian Andrzej Siewior [this message] 2018-06-04 10:25 ` [PATCH 1/5 v2] " Sebastian Andrzej Siewior 2018-06-04 10:27 ` [PATCH 1.5/5] alpha: atomic: provide asm for the fastpath for _atomic_dec_and_lock_irqsave Sebastian Andrzej Siewior 2018-06-04 11:48 ` Peter Zijlstra 2018-06-04 12:55 ` Sebastian Andrzej Siewior 2018-06-06 11:18 ` [PATCH 0.5/5] alpha: remove custom dec_and_lock() implementation Sebastian Andrzej Siewior 2018-06-06 11:21 ` Sebastian Andrzej Siewior 2018-06-06 11:59 ` Peter Zijlstra 2018-06-12 21:36 ` [tip:locking/urgent] alpha: Remove " tip-bot for Sebastian Andrzej Siewior 2018-05-04 15:45 ` [PATCH 2/5] mm/backing-dev: Use irqsave variant of atomic_dec_and_lock() Sebastian Andrzej Siewior 2018-05-04 15:45 ` [PATCH 3/5] kernel/user: " Sebastian Andrzej Siewior 2018-05-04 15:45 ` [PATCH 4/5] drivers/md/raid5: " Sebastian Andrzej Siewior 2018-05-04 15:45 ` [PATCH 5/5] drivers/md/raid5: Do not disable irq on release_inactive_stripe_list() call Sebastian Andrzej Siewior 2018-05-04 15:54 ` Introduce atomic_dec_and_lock_irqsave() Peter Zijlstra 2018-05-04 16:07 ` Sebastian Andrzej Siewior 2018-05-04 16:21 ` Peter Zijlstra 2018-05-04 16:26 ` Al Viro 2018-05-04 16:38 ` Peter Zijlstra 2018-05-23 13:02 ` Peter Zijlstra 2018-05-30 9:26 ` Sebastian Andrzej Siewior
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20180604102559.2ynbassthjzva62l@linutronix.de \ --to=bigeasy@linutronix.de \ --cc=anna-maria@linutronix.de \ --cc=ink@jurassic.park.msu.ru \ --cc=linux-alpha@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=linux-raid@vger.kernel.org \ --cc=mattst88@gmail.com \ --cc=mingo@redhat.com \ --cc=peterz@infradead.org \ --cc=rth@twiddle.net \ --cc=shli@kernel.org \ --cc=tglx@linutronix.de \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.