diff mbox series

[v2,1/5] blkdebug: refactor removal of a suspended request

Message ID 20210507151203.39643-2-eesposit@redhat.com
State New
Headers show
Series blkdebug: fix racing condition when iterating on | expand

Commit Message

Emanuele Giuseppe Esposito May 7, 2021, 3:11 p.m. UTC 
Extract to a separate function.  Do not rely on FOREACH_SAFE, which is
only "safe" if the *current* node is removed---not if another node is
removed.  Instead, just walk the entire list from the beginning when
asked to resume all suspended requests with a given tag.

Co-developed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block/blkdebug.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)
diff mbox series

Patch

diff --git a/block/blkdebug.c b/block/blkdebug.c
index 2c0b9b0ee8..8f19d991fa 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -793,7 +793,6 @@  static void suspend_request(BlockDriverState *bs, BlkdebugRule *rule)
         printf("blkdebug: Resuming request '%s'\n", r.tag);
     }
 
-    QLIST_REMOVE(&r, next);
     g_free(r.tag);
 }
 
@@ -869,25 +868,35 @@  static int blkdebug_debug_breakpoint(BlockDriverState *bs, const char *event,
     return 0;
 }
 
-static int blkdebug_debug_resume(BlockDriverState *bs, const char *tag)
+static int resume_req_by_tag(BDRVBlkdebugState *s, const char *tag, bool all)
 {
-    BDRVBlkdebugState *s = bs->opaque;
-    BlkdebugSuspendedReq *r, *next;
+    BlkdebugSuspendedReq *r;
 
-    QLIST_FOREACH_SAFE(r, &s->suspended_reqs, next, next) {
+retry:
+    QLIST_FOREACH(r, &s->suspended_reqs, next) {
         if (!strcmp(r->tag, tag)) {
+            QLIST_REMOVE(r, next);
             qemu_coroutine_enter(r->co);
+            if (all) {
+                goto retry;
+            }
             return 0;
         }
     }
     return -ENOENT;
 }
 
+static int blkdebug_debug_resume(BlockDriverState *bs, const char *tag)
+{
+    BDRVBlkdebugState *s = bs->opaque;
+
+    return resume_req_by_tag(s, tag, false);
+}
+
 static int blkdebug_debug_remove_breakpoint(BlockDriverState *bs,
                                             const char *tag)
 {
     BDRVBlkdebugState *s = bs->opaque;
-    BlkdebugSuspendedReq *r, *r_next;
     BlkdebugRule *rule, *next;
     int i, ret = -ENOENT;
 
@@ -900,11 +909,8 @@  static int blkdebug_debug_remove_breakpoint(BlockDriverState *bs,
             }
         }
     }
-    QLIST_FOREACH_SAFE(r, &s->suspended_reqs, next, r_next) {
-        if (!strcmp(r->tag, tag)) {
-            qemu_coroutine_enter(r->co);
-            ret = 0;
-        }
+    if (resume_req_by_tag(s, tag, true) == 0) {
+        ret = 0;
     }
     return ret;
 }