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DEBUG: threads: display held locks in threads dumps

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Based on the lock history, we can spot some locks that are still held
by checking the last operation that happened on them: if it's not an
unlock, then we know the lock is held. In this case we append the list
after "locked:" with their label and state like below:

  U:QUEUE S:IDLE_CONNS U:IDLE_CONNS R:TASK_WQ U:TASK_WQ S:QUEUE S:QUEUE S:QUEUE locked: QUEUE(S)
  S:IDLE_CONNS U:IDLE_CONNS S:TASK_RQ U:TASK_RQ S:QUEUE U:QUEUE S:IDLE_CONNS locked: IDLE_CONNS(S)
  R:TASK_WQ S:TASK_WQ R:TASK_WQ S:TASK_WQ R:TASK_WQ S:TASK_WQ R:TASK_WQ locked: TASK_WQ(R)
  W:STK_TABLE W:STK_TABLE_UPDT U:STK_TABLE_UPDT W:STK_TABLE W:STK_TABLE_UPDT U:STK_TABLE_UPDT W:STK_TABLE W:STK_TABLE_UPDT locked: STK_TABLE(W) STK_TABLE_UPDT(W)

The format is slightly different (label(status)) so as to easily
differentiate them visually from the history.
This commit is contained in:
Willy Tarreau 2025-05-06 05:11:56 +02:00
parent feaac66b5e
commit 3bb6eea6d5
1 changed files with 25 additions and 1 deletions
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26
src/debug.c
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@ -355,7 +355,8 @@ void ha_thread_dump_one(struct buffer *buf, int is_caller)
#if defined(USE_THREAD) && ((DEBUG_THREAD > 0) || defined(DEBUG_FULL))
/* List the lock history */
if (th_ctx->lock_history) {
int lkh, lkl;
int lkh, lkl, lbl;
int done;
chunk_appendf(buf, " lock_hist:");
for (lkl = 7; lkl >= 0; lkl--) {
@ -365,6 +366,29 @@ void ha_thread_dump_one(struct buffer *buf, int is_caller)
chunk_appendf(buf, " %c:%s",
"URSW"[lkh & 3], lock_label((lkh >> 2) - 1));
}
/* now rescan the list to only show those that remain */
done = 0;
for (lbl = 0; lbl < LOCK_LABELS; lbl++) {
/* find the latest occurrence of each label */
for (lkl = 0; lkl < 8; lkl++) {
lkh = (th_ctx->lock_history >> (lkl * 8)) & 0xff;
if (!lkh)
continue;
if ((lkh >> 2) == lbl)
break;
}
if (lkl == 8) // not found
continue;
if ((lkh & 3) == _LK_UN)
continue;
if (!done)
chunk_appendf(buf, " locked:");
chunk_appendf(buf, " %s(%c)",
lock_label((lkh >> 2) - 1),
"URSW"[lkh & 3]);
done++;
}
chunk_appendf(buf, "\n");
}
#endif