stack: use list_head for managing frames

PROBLEM
--------

statedump requests that traverse call frames of all call stacks in
execution may race with a STACK_RESET on a stack.  This could crash the
corresponding glusterfs process. For e.g, recently we observed this in a
regression test case tests/basic/afr/sparse-self-heal.t.

FIX
---

gf_proc_dump_pending_frames takes a (TRY_LOCK) call_pool->lock before
iterating through call frames of all call stacks in progress.  With this
fix, STACK_RESET removes its call frames under the same lock.

Additional info
----------------

This fix makes call_stack_t to use struct list_head in place of custom
doubly-linked list implementation. This makes call_frame_t manipulation
easier to maintain in the context of STACK_WIND et al.

BUG: 1229658
Change-Id: I7e43bccd3994cd9184ab982dba3dbc10618f0d94
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/11095
Reviewed-by: Niels de Vos <ndevos@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: NetBSD Build System <jenkins@build.gluster.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/xlators/features/protect/src/prot_client.c b/xlators/features/protect/src/prot_client.c
index dde3abdadc8..79636410b94 100644
--- a/xlators/features/protect/src/prot_client.c
+++ b/xlators/features/protect/src/prot_client.c
@@ -35,10 +35,9 @@ pcli_print_trace (char *name, call_frame_t *frame)
         int     i;
 
         gf_log (name, GF_LOG_INFO, "Translator stack:");
-        while (frame) {
+        list_for_each_entry (frame, &frame->root->myframes, frames) {
                 gf_log (name, GF_LOG_INFO, "%s (%s)",
                         frame->wind_from, frame->this->name);
-                frame = frame->next;
         }
 
         size = backtrace (frames, NUM_FRAMES);
@@ -77,7 +76,7 @@ pcli_rename (call_frame_t *frame, xlator_t *this, loc_t *oldloc,
         if (value != PROT_ACT_NONE) {
                 gf_log (this->name, GF_LOG_WARNING,
                         "got rename for protected %s", oldloc->path);
-                pcli_print_trace (this->name, frame->next);
+                pcli_print_trace (this->name, frame);
                 if (value == PROT_ACT_REJECT) {
                         STACK_UNWIND_STRICT (rename, frame, -1, EPERM,
                                              NULL, NULL, NULL, NULL, NULL,
@@ -161,7 +160,7 @@ pcli_unlink (call_frame_t *frame, xlator_t *this, loc_t *loc, int xflag,
         if (value != PROT_ACT_NONE) {
                 gf_log (this->name, GF_LOG_WARNING,
                         "got unlink for protected %s", loc->path);
-                pcli_print_trace(this->name,frame->next);
+                pcli_print_trace(this->name, frame);
                 if (value == PROT_ACT_REJECT) {
                         STACK_UNWIND_STRICT (unlink, frame, -1, EPERM,
                                              NULL, NULL, NULL);