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MFC r326657:

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Fix livelock in ufsdirhash_create().
This commit is contained in:
Konstantin Belousov 2017-12-14 11:45:02 +00:00
parent 56580f3f6d
commit f4c225ae42
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/stable/10/; revision=326846
1 changed files with 9 additions and 3 deletions
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12
sys/ufs/ufs/ufs_dirhash.c
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@ -189,9 +189,11 @@ ufsdirhash_create(struct inode *ip)
struct dirhash *ndh;
struct dirhash *dh;
struct vnode *vp;
bool excl;
ndh = dh = NULL;
vp = ip->i_vnode;
excl = false;
for (;;) {
/* Racy check for i_dirhash to prefetch a dirhash structure. */
if (ip->i_dirhash == NULL && ndh == NULL) {
@ -228,8 +230,11 @@ ufsdirhash_create(struct inode *ip)
ufsdirhash_hold(dh);
VI_UNLOCK(vp);
/* Acquire a shared lock on existing hashes. */
sx_slock(&dh->dh_lock);
/* Acquire a lock on existing hashes. */
if (excl)
sx_xlock(&dh->dh_lock);
else
sx_slock(&dh->dh_lock);
/* The hash could've been recycled while we were waiting. */
VI_LOCK(vp);
@ -250,9 +255,10 @@ ufsdirhash_create(struct inode *ip)
* so we can recreate it. If we fail the upgrade, drop our
* lock and try again.
*/
if (sx_try_upgrade(&dh->dh_lock))
if (excl || sx_try_upgrade(&dh->dh_lock))
break;
sx_sunlock(&dh->dh_lock);
excl = true;
}
/* Free the preallocated structure if it was not necessary. */
if (ndh) {