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locking/rwsem: Make rwsem->owner an atomic_long_t

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The rwsem->owner contains not just the task structure pointer, it also
holds some flags for storing the current state of the rwsem. Some of
the flags may have to be atomically updated. To reflect the new reality,
the owner is now changed to an atomic_long_t type.

New helper functions are added to properly separate out the task
structure pointer and the embedded flags.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Link: https://lkml.kernel.org/r/20190520205918.22251-14-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Waiman Long
2019-05-20 16:59:12 -04:00
committed by Ingo Molnar
parent cf69482d62
commit 94a9717b3c
3 changed files with 88 additions and 52 deletions
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11
include/linux/rwsem.h
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@@ -35,10 +35,11 @@
struct rw_semaphore {
atomic_long_t count;
/*
* Write owner or one of the read owners. Can be used as a
* speculative check to see if the owner is running on the cpu.
* Write owner or one of the read owners as well flags regarding
* the current state of the rwsem. Can be used as a speculative
* check to see if the write owner is running on the cpu.
*/
struct task_struct *owner;
atomic_long_t owner;
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
struct optimistic_spin_queue osq; /* spinner MCS lock */
#endif
@@ -53,7 +54,7 @@ struct rw_semaphore {
* Setting all bits of the owner field except bit 0 will indicate
* that the rwsem is writer-owned with an unknown owner.
*/
#define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-2L)
#define RWSEM_OWNER_UNKNOWN (-2L)
/* In all implementations count != 0 means locked */
static inline int rwsem_is_locked(struct rw_semaphore *sem)
@@ -80,7 +81,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
#define __RWSEM_INITIALIZER(name) \
{ __RWSEM_INIT_COUNT(name), \
.owner = NULL, \
.owner = ATOMIC_LONG_INIT(0), \
.wait_list = LIST_HEAD_INIT((name).wait_list), \
.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
__RWSEM_OPT_INIT(name) \