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BUG/MEDIUM: threads: Fix the exit condition of the thread barrier

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In thread_sync_barrier, we exit when all threads have set their own bit in the
barrier mask. It is done by comparing it to all_threads_mask. But we must not
use a simple equality to do so, becaue all_threads_mask may change. Since commit
ba86c6c25 ("MINOR: threads: Be sure to remove threads from all_threads_mask on
exit"), when a thread exit, its bit is removed from all_threads_mask. Instead,
we must use a bitwise AND to test is all bits of all_threads_mask are set.

This also requires that all_threads_mask is set to volatile if we want to
catch changes.

This patch must be backported in 1.8.
This commit is contained in:
Christopher Faulet 2018-07-20 09:31:53 +02:00 committed by Willy Tarreau
parent 20761453fb
commit ddb6c16576
2 changed files with 3 additions and 3 deletions
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2
include/common/hathreads.h
View File

@ -260,7 +260,7 @@ void thread_exit_sync(void);
int thread_no_sync(void);
int thread_need_sync(void);
extern unsigned long all_threads_mask;
extern volatile unsigned long all_threads_mask;
#define ha_sigmask(how, set, oldset) pthread_sigmask(how, set, oldset)

4
src/hathreads.c
View File

@ -31,7 +31,7 @@ void thread_sync_io_handler(int fd)
static HA_SPINLOCK_T sync_lock;
static int threads_sync_pipe[2];
static unsigned long threads_want_sync = 0;
unsigned long all_threads_mask = 0;
volatile unsigned long all_threads_mask = 0;
#if defined(DEBUG_THREAD) || defined(DEBUG_FULL)
struct lock_stat lock_stats[LOCK_LABELS];
@ -106,7 +106,7 @@ static inline void thread_sync_barrier(volatile unsigned long *barrier)
HA_ATOMIC_CAS(barrier, &old, 0);
HA_ATOMIC_OR(barrier, tid_bit);
while (*barrier != all_threads_mask)
while ((*barrier & all_threads_mask) != all_threads_mask)
pl_cpu_relax();
}