From 9771d9b3779d1f8149f04e70f89fd04f5600051e Mon Sep 17 00:00:00 2001 From: Anna-Maria Gleixner Date: Tue, 12 Jun 2018 18:16:20 +0200 Subject: [PATCH] BACKPORT: atomic: Add irqsave variant of atomic_dec_and_lock() 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. Signed-off-by: Anna-Maria Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r20180612161621.22645-3-bigeasy@linutronix.de (cherry picked from commit ccfbb5bed407053b27492a9adc06064d949a9aa6) BUG: 137270441 Change-Id: I49051801a73ac0de11d71bfa23930ce4826f7c61 Signed-off-by: Satya Tangirala --- include/linux/spinlock.h | 5 +++++ lib/dec_and_lock.c | 16 ++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 341e1a12bfc7..b5a6719c5b04 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -421,4 +421,9 @@ 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))) + #endif /* __LINUX_SPINLOCK_H */ 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);