Revert "BUG/MEDIUM: lists: Lock the element while we check if it is in a list."
This reverts previous commit 347bbf79d20e1cff57075a8a378355dfac2475e2i.
The original code was correct. This patch resulted from a mistaken analysis
and breaks the scheduler:
########################## Starting vtest ##########################
Testing with haproxy version: 2.2-dev11-90b7d9-23
# top TEST reg-tests/lua/close_wait_lf.vtc TIMED OUT (kill -9)
# top TEST reg-tests/lua/close_wait_lf.vtc FAILED (10.008) signal=9
1 tests failed, 0 tests skipped, 88 tests passed
Program terminated with signal SIGABRT, Aborted.
[Current thread is 1 (Thread 0x7fb0dac2c700 (LWP 11292))]
(gdb) bt
#0 0x00007fb0e7c143f8 in raise () from /lib64/libc.so.6
#1 0x00007fb0e7c15ffa in abort () from /lib64/libc.so.6
#2 0x000000000053f5d6 in ha_panic () at src/debug.c:269
#3 0x00000000005a6248 in wdt_handler (sig=14, si=<optimized out>, arg=<optimized out>) at src/wdt.c:119
#4 <signal handler called>
#5 0x00000000004fbccd in tasklet_wakeup (tl=0x1b5abc0) at include/haproxy/task.h:351
#6 listener_accept (fd=<optimized out>) at src/listener.c:999
#7 0x00000000004262df in fd_update_events (evts=<optimized out>, fd=6) at include/haproxy/fd.h:418
#8 _do_poll (p=<optimized out>, exp=<optimized out>, wake=<optimized out>) at src/ev_epoll.c:251
#9 0x0000000000548d0f in run_poll_loop () at src/haproxy.c:2949
#10 0x000000000054908b in run_thread_poll_loop (data=<optimized out>) at src/haproxy.c:3067
#11 0x00007fb0e902b684 in start_thread () from /lib64/libpthread.so.0
#12 0x00007fb0e7ce5eed in clone () from /lib64/libc.so.6
(gdb) up
#5 0x00000000004fbccd in tasklet_wakeup (tl=0x1b5abc0) at include/haproxy/task.h:351
351 if (MT_LIST_ADDQ(&task_per_thread[tl->tid].shared_tasklet_list, (struct mt_list *)&tl->list) == 1) {
If the commit above is ever backported, this one must be as well!
diff --git a/include/haproxy/list.h b/include/haproxy/list.h
index 7f05be2..2f2699f 100644
--- a/include/haproxy/list.h
+++ b/include/haproxy/list.h
@@ -230,8 +230,8 @@
int _ret = 0; \
struct mt_list *lh = (_lh), *el = (_el); \
while (1) { \
- struct mt_list *n, *n2; \
- struct mt_list *p, *p2; \
+ struct mt_list *n; \
+ struct mt_list *p; \
n = _HA_ATOMIC_XCHG(&(lh)->next, MT_LIST_BUSY); \
if (n == MT_LIST_BUSY) \
continue; \
@@ -241,25 +241,11 @@
__ha_barrier_store(); \
continue; \
} \
- n2 = _HA_ATOMIC_XCHG(&(el)->next, MT_LIST_BUSY); \
- if (n2 != (el)) { \
+ if ((el)->next != (el) || (el)->prev != (el)) { \
(n)->prev = p; \
(lh)->next = n; \
- (el)->next = n2; \
- if (n2 == MT_LIST_BUSY) \
- continue; \
break; \
} \
- p2 = _HA_ATOMIC_XCHG(&(el)->prev, MT_LIST_BUSY); \
- if (p2 != (el)) { \
- n->prev = p; \
- (lh)->next = n; \
- (el)->next = n2; \
- (el)->prev = p2; \
- if (p2 == MT_LIST_BUSY) \
- continue; \
- break; \
- } \
(el)->next = n; \
(el)->prev = p; \
__ha_barrier_store(); \
@@ -283,8 +269,8 @@
int _ret = 0; \
struct mt_list *lh = (_lh), *el = (_el); \
while (1) { \
- struct mt_list *n, *n2; \
- struct mt_list *p, *p2; \
+ struct mt_list *n; \
+ struct mt_list *p; \
p = _HA_ATOMIC_XCHG(&(lh)->prev, MT_LIST_BUSY); \
if (p == MT_LIST_BUSY) \
continue; \
@@ -294,23 +280,9 @@
__ha_barrier_store(); \
continue; \
} \
- n2 = _HA_ATOMIC_XCHG(&(el)->next, MT_LIST_BUSY); \
- if (n2 != (el)) { \
- p->next = n; \
- (lh)->prev = p; \
- (el)->next = n2; \
- if (n2 == MT_LIST_BUSY) \
- continue; \
- break; \
- } \
- p2 = _HA_ATOMIC_XCHG(&(el)->prev, MT_LIST_BUSY); \
- if (p2 != (el)) { \
+ if ((el)->next != (el) || (el)->prev != (el)) { \
p->next = n; \
(lh)->prev = p; \
- (el)->next = n2; \
- (el)->prev = p2; \
- if (p2 == MT_LIST_BUSY) \
- continue; \
break; \
} \
(el)->next = n; \