LU-8354 ldlm: soft lockup in ldlm_plain_compat_queue

commit c09b59bb958f3e089b95dd9492cc1bef17cb3782
LU-3963 ldlm: convert to linux list api

breaks loop iteration optimisation.
tmp variable is modified later to skip already
processed locks from the same mode group.

Change-Id: I4dd493d6bd5bb2ac54801cb289dc89efabdfa920
Seagate-bug-id: MRP-3611
Signed-off-by: Andriy Skulysh <andriy.skulysh@seagate.com>
Reviewed-on: http://review.whamcloud.com/21093
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/ldlm/ldlm_plain.c b/lustre/ldlm/ldlm_plain.c
index 6a99608..bbc355f 100644 (file)
--- a/lustre/ldlm/ldlm_plain.c
+++ b/lustre/ldlm/ldlm_plain.c
@@ -73,14 +73,14 @@ ldlm_plain_compat_queue(struct list_head *queue, struct ldlm_lock *req,
                        struct list_head *work_list)
 {
        enum ldlm_mode req_mode = req->l_req_mode;
                        struct list_head *work_list)
 {
        enum ldlm_mode req_mode = req->l_req_mode;

-       struct ldlm_lock *lock;
-       struct list_head *tmp;
+       struct ldlm_lock *lock, *next_lock;

        int compat = 1;
        ENTRY;
 
        lockmode_verify(req_mode);
 
        int compat = 1;
        ENTRY;
 
        lockmode_verify(req_mode);
 

-       list_for_each_entry(lock, queue, l_res_link) {
+       list_for_each_entry_safe(lock, next_lock, queue, l_res_link) {
+

                /* We stop walking the queue if we hit ourselves so we don't
                 * take conflicting locks enqueued after us into account,
                 * or we'd wait forever. */
                /* We stop walking the queue if we hit ourselves so we don't
                 * take conflicting locks enqueued after us into account,
                 * or we'd wait forever. */


@@ -88,8 +88,10 @@ ldlm_plain_compat_queue(struct list_head *queue, struct ldlm_lock *req,
                        RETURN(compat);
 
                /* Advance loop cursor to last lock of mode group. */
                        RETURN(compat);
 
                /* Advance loop cursor to last lock of mode group. */

-               tmp = &list_entry(lock->l_sl_mode.prev, struct ldlm_lock,
-                                 l_sl_mode)->l_res_link;
+               next_lock = list_entry(list_entry(lock->l_sl_mode.prev,
+                                                 struct ldlm_lock,
+                                                 l_sl_mode)->l_res_link.next,
+                                      struct ldlm_lock, l_res_link);

 
                if (lockmode_compat(lock->l_req_mode, req_mode))
                         continue;
 
                if (lockmode_compat(lock->l_req_mode, req_mode))
                         continue;