Archive-Team
/
zfs
2
0
Fork 0
Code Issues Pull Requests Packages Projects Releases 103 Wiki Activity

Don't take spin lock on rwlock owner 

The spin lock around rw_owner is completely unnecessary. The reason is that it
is only modified in the down_write context. If you race against another thread
modifying it, that means that you aren't holding the rwlock, so taking the
spin lock don't eliminate the race.

Also, we only check rw_owner in RW_WRITE_HELD because spl_rwsem_is_locked
is unnecessary and might need to take spin lock.

Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #473
This commit is contained in:
Chunwei Chen 2015-09-01 21:55:06 +08:00 committed by Brian Behlendorf
parent 3e1e4c735c
commit 4f8e643afe
1 changed files with 4 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
include/sys/rwlock.h
View File

@ -50,34 +50,19 @@ typedef struct {
static inline void
spl_rw_set_owner(krwlock_t *rwp)
{
unsigned long flags;
spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags);
rwp->rw_owner = current;
spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
rwp->rw_owner = current;
}
static inline void
spl_rw_clear_owner(krwlock_t *rwp)
{
unsigned long flags;
spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags);
rwp->rw_owner = NULL;
spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
rwp->rw_owner = NULL;
}
static inline kthread_t *
rw_owner(krwlock_t *rwp)
{
unsigned long flags;
kthread_t *owner;
spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags);
owner = rwp->rw_owner;
spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
return owner;
return rwp->rw_owner;
}
static inline int
@ -89,7 +74,7 @@ RW_READ_HELD(krwlock_t *rwp)
static inline int
RW_WRITE_HELD(krwlock_t *rwp)
{
return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == current);
return (rw_owner(rwp) == current);
}
static inline int