commit 0a6b4a2c54784c90ec1b762cb6880ebc745658e9 (patch)
parent 461c3d4 use _POSIX_C_SOURCE=200809L
tree 025adccf5797753079673dc7dd7b463c046e8bfb
author Eric Wong <bofh@yhbt.net> 2023-03-19 20:24:29 +0000
committer Eric Wong <bofh@yhbt.net> 2023-05-11 21:27:08 +0000
workaround for time(2) being non-monotonic
Apparently, time(2) may go backwards in the first 1 - 2.5ms of
every second since Linux + glibc 2.31+ (and some proprietary
OSes). Use clock_gettime(2) with CLOCK_REALTIME to workaround
the problem at the cost of a slight performance hit(*). While git
will likely use gettimeofday(2) for compatibility with
proprietary OSes, gettimeofday(2) was declared obsolete in
POSIX.1-2008 and we don't support proprietary OSes.
(*) https://inbox.sourceware.org/libc-alpha/87ttywq0je.fsf@oldenburg.str.redhat.com/
Link: https://lore.kernel.org/git/20230319064353.686226-3-eggert@cs.ucla.edu/T/
---
ext/clogger_ext/clogger.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/ext/clogger_ext/clogger.c b/ext/clogger_ext/clogger.c
index 7989472..23aea39 100644
--- a/ext/clogger_ext/clogger.c
+++ b/ext/clogger_ext/clogger.c
@@ -475,9 +475,21 @@ static void append_request_length(struct clogger *c)
}
}
+/*
+ * time(2) may slip backwards, so use CLOCK_REALTIME for accuracy
+ * https://lore.kernel.org/git/20230319064353.686226-3-eggert@cs.ucla.edu/T/
+ */
+static time_t cur_time(void)
+{
+ struct timespec now;
+
+ (void)clock_gettime(CLOCK_REALTIME, &now);
+ return now.tv_sec;
+}
+
static long local_gmtoffset(struct tm *tm)
{
- time_t t = time(NULL);
+ time_t t = cur_time();
tzset();
localtime_r(&t, tm);
@@ -537,7 +549,7 @@ static void append_time_utc(struct clogger *c)
char buf[sizeof("01/Jan/1970:00:00:00 +0000")];
struct tm tm;
int nr;
- time_t t = time(NULL);
+ time_t t = cur_time();
gmtime_r(&t, &tm);
nr = snprintf(buf, sizeof(buf),
@@ -556,7 +568,7 @@ append_time(struct clogger *c, enum clogger_opcode op, VALUE fmt, VALUE buf)
size_t buf_size = RSTRING_LEN(buf) + 1; /* "\0" */
size_t nr;
struct tm tmp;
- time_t t = time(NULL);
+ time_t t = cur_time();
if (op == CL_OP_TIME_LOCAL)
localtime_r(&t, &tmp);
glossary
--------
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git clone http://yhbt.net/clogger.git