Commit 83ced169 authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Ingo Molnar
Browse files

locking/rwsem-xadd: Add killable versions of rwsem_down_read_failed() 



Rename rwsem_down_read_failed() in __rwsem_down_read_failed_common()
and teach it to abort waiting in case of pending signals and killable
state argument passed.

Note, that we shouldn't wake anybody up in EINTR path, as:

We check for (waiter.task) under spinlock before we go to out_nolock
path. Current task wasn't able to be woken up, so there are
a writer, owning the sem, or a writer, which is the first waiter.
In the both cases we shouldn't wake anybody. If there is a writer,
owning the sem, and we were the only waiter, remove RWSEM_WAITING_BIAS,
as there are no waiters anymore.

Signed-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arnd@arndb.de
Cc: avagin@virtuozzo.com
Cc: davem@davemloft.net
Cc: fenghua.yu@intel.com
Cc: gorcunov@virtuozzo.com
Cc: heiko.carstens@de.ibm.com
Cc: hpa@zytor.com
Cc: ink@jurassic.park.msu.ru
Cc: mattst88@gmail.com
Cc: rth@twiddle.net
Cc: schwidefsky@de.ibm.com
Cc: tony.luck@intel.com
Link: http://lkml.kernel.org/r/149789534632.9059.2901382369609922565.stgit@localhost.localdomain


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0aa1125f

include/linux/rwsem.h

+1 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ struct rw_semaphore { 
};



extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);

extern struct rw_semaphore *rwsem_down_read_failed_killable(struct rw_semaphore *sem);

extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);

extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem);

extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);

kernel/locking/rwsem-xadd.c

+30 −3
Original line number Diff line number Diff line
@@ -221,8 +221,8 @@ static void __rwsem_mark_wake(struct rw_semaphore *sem, 
/*

 * Wait for the read lock to be granted

 */

__visible

struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)

static inline struct rw_semaphore __sched *

__rwsem_down_read_failed_common(struct rw_semaphore *sem, int state)

{

	long count, adjustment = -RWSEM_ACTIVE_READ_BIAS;

	struct rwsem_waiter waiter;
@@ -255,17 +255,44 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem) 


	/* wait to be given the lock */

	while (true) {

		set_current_state(TASK_UNINTERRUPTIBLE);

		set_current_state(state);

		if (!waiter.task)

			break;

		if (signal_pending_state(state, current)) {

			raw_spin_lock_irq(&sem->wait_lock);

			if (waiter.task)

				goto out_nolock;

			raw_spin_unlock_irq(&sem->wait_lock);

			break;

		}

		schedule();

	}



	__set_current_state(TASK_RUNNING);

	return sem;

out_nolock:

	list_del(&waiter.list);

	if (list_empty(&sem->wait_list))

		atomic_long_add(-RWSEM_WAITING_BIAS, &sem->count);

	raw_spin_unlock_irq(&sem->wait_lock);

	__set_current_state(TASK_RUNNING);

	return ERR_PTR(-EINTR);

}



__visible struct rw_semaphore * __sched

rwsem_down_read_failed(struct rw_semaphore *sem)

{

	return __rwsem_down_read_failed_common(sem, TASK_UNINTERRUPTIBLE);

}

EXPORT_SYMBOL(rwsem_down_read_failed);



__visible struct rw_semaphore * __sched

rwsem_down_read_failed_killable(struct rw_semaphore *sem)

{

	return __rwsem_down_read_failed_common(sem, TASK_KILLABLE);

}

EXPORT_SYMBOL(rwsem_down_read_failed_killable);



/*

 * This function must be called with the sem->wait_lock held to prevent

 * race conditions between checking the rwsem wait list and setting the

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