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Change server.daylight_active to an atomic variable (#876)

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We are updating this variable in the main thread, and the
child threads can printing the logs at the same time. This
generating a warning in SANITIZER=thread:
```
WARNING: ThreadSanitizer: data race (pid=74208)
  Read of size 4 at 0x000102875c10 by thread T3:
    #0 serverLogRaw <null>:52173615 (valkey-server:x86_64+0x10003c556)
    #1 _serverLog <null>:52173615 (valkey-server:x86_64+0x10003ca89)
    #2 bioProcessBackgroundJobs <null>:52173615 (valkey-server:x86_64+0x1001402c9)

  Previous write of size 4 at 0x000102875c10 by main thread (mutexes: write M0):
    #0 afterSleep <null>:52173615 (valkey-server:x86_64+0x10004989b)
    #1 aeProcessEvents <null>:52173615 (valkey-server:x86_64+0x100031e52)
    #2 main <null>:52173615 (valkey-server:x86_64+0x100064a3c)
    #3 start <null>:52173615 (dyld:x86_64+0xfffffffffff5c365)
    #4 start <null>:52173615 (dyld:x86_64+0xfffffffffff5c365)
```

The refresh of daylight_active is not real time, we update
it in aftersleep, so we don't need a strong synchronization,
so using memory_order_relaxed. But also noted we are doing
load/store operations only for daylight_active, which is an
aligned 32-bit integer, so using memory_order_relaxed will
not provide more consistency than what we have today.

So this is just a cleanup that to clear the warning.

Signed-off-by: Binbin <binloveplay1314@qq.com>
This commit is contained in:
Binbin 2024-08-14 13:08:20 +08:00 committed by GitHub
parent 6cb86fff51
commit 370bdb3e46
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GPG Key ID: B5690EEEBB952194
2 changed files with 4 additions and 3 deletions
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5
src/server.c
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@ -131,10 +131,11 @@ void serverLogRaw(int level, const char *msg) {
struct timeval tv;
int role_char;
pid_t pid = getpid();
int daylight_active = atomic_load_explicit(&server.daylight_active, memory_order_relaxed);
gettimeofday(&tv, NULL);
struct tm tm;
nolocks_localtime(&tm, tv.tv_sec, server.timezone, server.daylight_active);
nolocks_localtime(&tm, tv.tv_sec, server.timezone, daylight_active);
off = strftime(buf, sizeof(buf), "%d %b %Y %H:%M:%S.", &tm);
snprintf(buf + off, sizeof(buf) - off, "%03d", (int)tv.tv_usec / 1000);
if (server.sentinel_mode) {
@ -1091,7 +1092,7 @@ static inline void updateCachedTimeWithUs(int update_daylight_info, const long l
struct tm tm;
time_t ut = server.unixtime;
localtime_r(&ut, &tm);
server.daylight_active = tm.tm_isdst;
atomic_store_explicit(&server.daylight_active, tm.tm_isdst, memory_order_relaxed);
}
}

2
src/server.h
View File

@ -2114,7 +2114,7 @@ struct valkeyServer {
/* time cache */
time_t unixtime; /* Unix time sampled every cron cycle. */
time_t timezone; /* Cached timezone. As set by tzset(). */
int daylight_active; /* Currently in daylight saving time. */
_Atomic int daylight_active; /* Currently in daylight saving time. */
mstime_t mstime; /* 'unixtime' in milliseconds. */
ustime_t ustime; /* 'unixtime' in microseconds. */
mstime_t cmd_time_snapshot; /* Time snapshot of the root execution nesting. */