From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 936266B0003 for ; Mon, 4 Jun 2018 06:26:07 -0400 (EDT) Received: by mail-wr0-f200.google.com with SMTP id p9-v6so14947552wrm.22 for ; Mon, 04 Jun 2018 03:26:07 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id z14-v6si11573836wrn.199.2018.06.04.03.26.05 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 04 Jun 2018 03:26:06 -0700 (PDT) Date: Mon, 4 Jun 2018 12:25:59 +0200 From: Sebastian Andrzej Siewior Subject: [PATCH 1/5 v2] spinlock: atomic_dec_and_lock: Add an irqsave variant Message-ID: <20180604102559.2ynbassthjzva62l@linutronix.de> References: <20180504154533.8833-1-bigeasy@linutronix.de> <20180504154533.8833-2-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20180504154533.8833-2-bigeasy@linutronix.de> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, Peter Zijlstra , Ingo Molnar , linux-mm@kvack.org, Shaohua Li , linux-raid@vger.kernel.org, Anna-Maria Gleixner , Richard Henderson , Ivan Kokshaysky , Matt Turner , linux-alpha@vger.kernel.org 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) [not the Alpha bits] Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: linux-alpha@vger.kernel.org Signed-off-by: Anna-Maria Gleixner [bigeasy: adding Alpha bits] Signed-off-by: Sebastian Andrzej Siewior --- v1=E2=80=A6v2: 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, spin= lock_t *lock); #define atomic_dec_and_lock(atomic, lock) \ __cond_lock(lock, _atomic_dec_and_lock(atomic, lock)) =20 +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 *l= ock) } =20 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); --=20 2.17.1