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authorSunil Mushran <sunil.mushran@oracle.com>2008-12-16 15:49:22 -0800
committerMark Fasheh <mfasheh@suse.com>2009-01-05 08:40:35 -0800
commitb0d4f817ba5de8adb875ace594554a96d7737710 (patch)
tree2e64d3240d6ad879c4ffa1c01ca1696abf3bb2fb /fs/ocfs2/dlm/dlmdebug.c
parentd4f7e650e55af6b235871126f747da88600e8040 (diff)
ocfs2/dlm: Fix race in adding/removing lockres' to/from the tracking list
This patch adds a new lock, dlm->tracking_lock, to protect adding/removing lockres' to/from the dlm->tracking_list. We were previously using dlm->spinlock for the same, but that proved inadequate as we could be freeing a lockres from a context that did not hold that lock. As the new lock only protects this list, we can explicitly take it when removing the lockres from the tracking list. This bug was exposed when testing multiple processes concurrently flock() the same file. Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Diffstat (limited to 'fs/ocfs2/dlm/dlmdebug.c')
-rw-r--r--fs/ocfs2/dlm/dlmdebug.c53
1 files changed, 24 insertions, 29 deletions
diff --git a/fs/ocfs2/dlm/dlmdebug.c b/fs/ocfs2/dlm/dlmdebug.c
index 1b81dcba175..b32f60a5acf 100644
--- a/fs/ocfs2/dlm/dlmdebug.c
+++ b/fs/ocfs2/dlm/dlmdebug.c
@@ -630,43 +630,38 @@ static void *lockres_seq_start(struct seq_file *m, loff_t *pos)
{
struct debug_lockres *dl = m->private;
struct dlm_ctxt *dlm = dl->dl_ctxt;
+ struct dlm_lock_resource *oldres = dl->dl_res;
struct dlm_lock_resource *res = NULL;
+ struct list_head *track_list;
- spin_lock(&dlm->spinlock);
+ spin_lock(&dlm->track_lock);
+ if (oldres)
+ track_list = &oldres->tracking;
+ else
+ track_list = &dlm->tracking_list;
- if (dl->dl_res) {
- list_for_each_entry(res, &dl->dl_res->tracking, tracking) {
- if (dl->dl_res) {
- dlm_lockres_put(dl->dl_res);
- dl->dl_res = NULL;
- }
- if (&res->tracking == &dlm->tracking_list) {
- mlog(0, "End of list found, %p\n", res);
- dl = NULL;
- break;
- }
+ list_for_each_entry(res, track_list, tracking) {
+ if (&res->tracking == &dlm->tracking_list)
+ res = NULL;
+ else
dlm_lockres_get(res);
- dl->dl_res = res;
- break;
- }
- } else {
- if (!list_empty(&dlm->tracking_list)) {
- list_for_each_entry(res, &dlm->tracking_list, tracking)
- break;
- dlm_lockres_get(res);
- dl->dl_res = res;
- } else
- dl = NULL;
+ break;
}
+ spin_unlock(&dlm->track_lock);
- if (dl) {
- spin_lock(&dl->dl_res->spinlock);
- dump_lockres(dl->dl_res, dl->dl_buf, dl->dl_len - 1);
- spin_unlock(&dl->dl_res->spinlock);
- }
+ if (oldres)
+ dlm_lockres_put(oldres);
- spin_unlock(&dlm->spinlock);
+ dl->dl_res = res;
+
+ if (res) {
+ spin_lock(&res->spinlock);
+ dump_lockres(res, dl->dl_buf, dl->dl_len - 1);
+ spin_unlock(&res->spinlock);
+ } else
+ dl = NULL;
+ /* passed to seq_show */
return dl;
}