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- Use an acquire barrier to increment f_count in fget_unlocked and

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remove the volatile cast.  Describe the reason in detail in a comment.

Discussed with:	bde, jhb
This commit is contained in:
Jeff Roberson 2009-06-02 06:55:32 +00:00
parent f08e28cfc6
commit f4471727f3
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=193301
1 changed files with 6 additions and 2 deletions
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8
sys/kern/kern_descrip.c
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@ -2075,9 +2075,13 @@ fget_unlocked(struct filedesc *fdp, int fd)
count = fp->f_count;
if (count == 0)
continue;
if (atomic_cmpset_int(&fp->f_count, count, count + 1) != 1)
/*
* Use an acquire barrier to prevent caching of fd_ofiles
* so it is refreshed for verification.
*/
if (atomic_cmpset_acq_int(&fp->f_count, count, count + 1) != 1)
continue;
if (fp == ((struct file *volatile*)fdp->fd_ofiles)[fd])
if (fp == fdp->fd_ofiles[fd])
break;
fdrop(fp, curthread);
}