2005-04-16 16:20:36 -06:00
|
|
|
/* rwsem-spinlock.h: fallback C implementation
|
|
|
|
|
*
|
|
|
|
|
* Copyright (c) 2001 David Howells (dhowells@redhat.com).
|
|
|
|
|
* - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
|
|
|
|
|
* - Derived also from comments by Linus
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#ifndef _LINUX_RWSEM_SPINLOCK_H
|
|
|
|
|
#define _LINUX_RWSEM_SPINLOCK_H
|
|
|
|
|
|
|
|
|
|
#ifndef _LINUX_RWSEM_H
|
|
|
|
|
#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifdef __KERNEL__
|
|
|
|
|
/*
|
|
|
|
|
* the rw-semaphore definition
|
2014-07-16 06:54:55 -06:00
|
|
|
* - if count is 0 then there are no active readers or writers
|
|
|
|
|
* - if count is +ve then that is the number of active readers
|
|
|
|
|
* - if count is -1 then there is one active writer
|
2005-04-16 16:20:36 -06:00
|
|
|
* - if wait_list is not empty, then there are processes waiting for the semaphore
|
|
|
|
|
*/
|
|
|
|
|
struct rw_semaphore {
|
2014-07-16 06:54:55 -06:00
|
|
|
__s32 count;
|
2010-02-24 01:54:54 -07:00
|
|
|
raw_spinlock_t wait_lock;
|
2005-04-16 16:20:36 -06:00
|
|
|
struct list_head wait_list;
|
2006-07-03 01:24:53 -06:00
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
|
|
|
struct lockdep_map dep_map;
|
|
|
|
|
#endif
|
2005-04-16 16:20:36 -06:00
|
|
|
};
|
|
|
|
|
|
2011-01-26 13:06:00 -07:00
|
|
|
#define RWSEM_UNLOCKED_VALUE 0x00000000
|
2006-07-03 01:24:53 -06:00
|
|
|
|
2008-02-13 16:03:15 -07:00
|
|
|
extern void __down_read(struct rw_semaphore *sem);
|
locking/rwsem-spinlock: Add killable versions of __down_read()
Rename __down_read() in __down_read_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 signal_pending_state() after (!waiter.task)
test and under spinlock. So, current task wasn't able to
be woken up. It may be in two cases: a writer is owner
of the sem, or a writer is a first waiter of the sem.
If a writer is owner of the sem, no one else may work
with it in parallel. It will wake somebody, when it
call up_write() or downgrade_write().
If a writer is the first waiter, it will be woken up,
when the last active reader releases the sem, and
sem->count became 0.
Also note, that set_current_state() may be moved down
to schedule() (after !waiter.task check), as all
assignments in this type of semaphore (including wake_up),
occur under spinlock, so we can't miss anything.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Peter 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/149789533283.9059.9829416940494747182.stgit@localhost.localdomain
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-19 12:02:12 -06:00
|
|
|
extern int __must_check __down_read_killable(struct rw_semaphore *sem);
|
2008-02-13 16:03:15 -07:00
|
|
|
extern int __down_read_trylock(struct rw_semaphore *sem);
|
|
|
|
|
extern void __down_write(struct rw_semaphore *sem);
|
2016-04-07 09:12:26 -06:00
|
|
|
extern int __must_check __down_write_killable(struct rw_semaphore *sem);
|
2008-02-13 16:03:15 -07:00
|
|
|
extern int __down_write_trylock(struct rw_semaphore *sem);
|
|
|
|
|
extern void __up_read(struct rw_semaphore *sem);
|
|
|
|
|
extern void __up_write(struct rw_semaphore *sem);
|
|
|
|
|
extern void __downgrade_write(struct rw_semaphore *sem);
|
2009-12-14 19:00:21 -07:00
|
|
|
extern int rwsem_is_locked(struct rw_semaphore *sem);
|
2005-10-29 19:15:44 -06:00
|
|
|
|
2005-04-16 16:20:36 -06:00
|
|
|
#endif /* __KERNEL__ */
|
|
|
|
|
#endif /* _LINUX_RWSEM_SPINLOCK_H */
|