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vlog: Avoid deadlock in vlog_init__() corner case.

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Anything inside vlog_init__() that tried to log a message was going to
deadlock, since it would hit pthread_once() recursively and wait for the
previous call to complete.  Unfortunately, there was a VLOG_ERR call inside
vlog_init__(), only called in the corner case where the system's clock was
wrong.

This fixes the problem by rearranging code so that the logging isn't
inside the "once-only" region.

Found by inspection.

Signed-off-by: Ben Pfaff <blp@nicira.com>
This commit is contained in:
Ben Pfaff
2013-12-05 16:59:13 -08:00
parent 1fe4c0a0ca
commit c3b758f6fe
1 changed files with 41 additions and 35 deletions
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76
lib/vlog.c
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@@ -592,46 +592,52 @@ vlog_disable_rate_limit(struct unixctl_conn *conn, int argc,
set_rate_limits(conn, argc, argv, false); set_rate_limits(conn, argc, argv, false);
} }
static void
vlog_init__(void)
{
static char *program_name_copy;
long long int now;
/* openlog() is allowed to keep the pointer passed in, without making a
* copy. The daemonize code sometimes frees and replaces 'program_name',
* so make a private copy just for openlog(). (We keep a pointer to the
* private copy to suppress memory leak warnings in case openlog() does
* make its own copy.) */
program_name_copy = program_name ? xstrdup(program_name) : NULL;
openlog(program_name_copy, LOG_NDELAY, LOG_DAEMON);
now = time_wall_msec();
if (now < 0) {
char *s = xastrftime_msec("%a, %d %b %Y %H:%M:%S", now, true);
VLOG_ERR("current time is negative: %s (%lld)", s, now);
free(s);
}
unixctl_command_register(
"vlog/set", "{spec | PATTERN:facility:pattern}",
1, INT_MAX, vlog_unixctl_set, NULL);
unixctl_command_register("vlog/list", "", 0, 0, vlog_unixctl_list, NULL);
unixctl_command_register("vlog/enable-rate-limit", "[module]...",
0, INT_MAX, vlog_enable_rate_limit, NULL);
unixctl_command_register("vlog/disable-rate-limit", "[module]...",
0, INT_MAX, vlog_disable_rate_limit, NULL);
unixctl_command_register("vlog/reopen", "", 0, 0,
vlog_unixctl_reopen, NULL);
}
/* Initializes the logging subsystem and registers its unixctl server /* Initializes the logging subsystem and registers its unixctl server
* commands. */ * commands. */
void void
vlog_init(void) vlog_init(void)
{ {
static pthread_once_t once = PTHREAD_ONCE_INIT; static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
pthread_once(&once, vlog_init__);
if (ovsthread_once_start(&once)) {
static char *program_name_copy;
long long int now;
/* Do initialization work that needs to be done before any logging
* occurs. We want to keep this really minimal because any attempt to
* log anything before calling ovsthread_once_done() will deadlock. */
/* openlog() is allowed to keep the pointer passed in, without making a
* copy. The daemonize code sometimes frees and replaces
* 'program_name', so make a private copy just for openlog(). (We keep
* a pointer to the private copy to suppress memory leak warnings in
* case openlog() does make its own copy.) */
program_name_copy = program_name ? xstrdup(program_name) : NULL;
openlog(program_name_copy, LOG_NDELAY, LOG_DAEMON);
ovsthread_once_done(&once);
/* Now do anything that we want to happen only once but doesn't have to
* finish before we start logging. */
now = time_wall_msec();
if (now < 0) {
char *s = xastrftime_msec("%a, %d %b %Y %H:%M:%S", now, true);
VLOG_ERR("current time is negative: %s (%lld)", s, now);
free(s);
}
unixctl_command_register(
"vlog/set", "{spec | PATTERN:facility:pattern}",
1, INT_MAX, vlog_unixctl_set, NULL);
unixctl_command_register("vlog/list", "", 0, 0, vlog_unixctl_list,
NULL);
unixctl_command_register("vlog/enable-rate-limit", "[module]...",
0, INT_MAX, vlog_enable_rate_limit, NULL);
unixctl_command_register("vlog/disable-rate-limit", "[module]...",
0, INT_MAX, vlog_disable_rate_limit, NULL);
unixctl_command_register("vlog/reopen", "", 0, 0,
vlog_unixctl_reopen, NULL);
}
} }
/* Enables VLF_FILE log output to be written asynchronously to disk. /* Enables VLF_FILE log output to be written asynchronously to disk.