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Code Issues Releases Activity

If the buffer lock has waiters after the buffer has changed identity then

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getnewbuf() needs to drop the buffer in order to wake waiters that might
sleep on the buffer in the context of the old identity.
This commit is contained in:
Tor Egge 2006-10-02 02:06:27 +00:00
parent 2eb6639bf4
commit 04aa807cb6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=162941
4 changed files with 38 additions and 0 deletions
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15
sys/kern/kern_lock.c
View File

@ -565,6 +565,21 @@ lockcount(lkp)
return (count);
}
/*
* Determine the number of waiters on a lock.
*/
int
lockwaiters(lkp)
struct lock *lkp;
{
int count;
mtx_lock(lkp->lk_interlock);
count = lkp->lk_waitcount;
mtx_unlock(lkp->lk_interlock);
return (count);
}
/*
* Print out information about state of a lock. Used by VOP_PRINT
* routines to display status about contained locks.

11
sys/kern/vfs_bio.c
View File

@ -1889,6 +1889,17 @@ getnewbuf(int slpflag, int slptimeo, int size, int maxsize)
goto restart;
}
/*
* Notify any waiters for the buffer lock about
* identity change by freeing the buffer.
*/
if (qindex == QUEUE_CLEAN && BUF_LOCKWAITERS(bp) > 0) {
bp->b_flags |= B_INVAL;
bfreekva(bp);
brelse(bp);
goto restart;
}
/*
* If we are overcomitted then recover the buffer and its
* KVM space. This occurs in rare situations when multiple

11
sys/sys/buf.h
View File

@ -371,6 +371,17 @@ BUF_REFCNT(struct buf *bp)
return ret;
}
/*
* Find out the number of waiters on a lock.
*/
static __inline int BUF_LOCKWAITERS(struct buf *);
static __inline int
BUF_LOCKWAITERS(struct buf *bp)
{
return (lockwaiters(&bp->b_lock));
}
#endif /* _KERNEL */
struct buf_queue_head {

1
sys/sys/lockmgr.h
View File

@ -203,6 +203,7 @@ void transferlockers(struct lock *, struct lock *);
void lockmgr_printinfo(struct lock *);
int lockstatus(struct lock *, struct thread *);
int lockcount(struct lock *);
int lockwaiters(struct lock *);
#ifdef DDB
int lockmgr_chain(struct thread *td, struct thread **ownerp);
#endif