[PATCH] log: setlogmask(0) can actually result in a system call, don't use it

[Stefano Brivio <sbrivio@redhat.com>]

Before commit 32d07f5e59f2 ("passt, pasta: Completely avoid dynamic
memory allocation"), we didn't store the current log mask in a
variable, and we fetched it using setlogmask(0) wherever needed.

But after that commit, we can just use our log_mask copy instead. And
we should: with recent glibc versions, setlogmask(0) actually results
in a system call, which causes a substantial overhead with high
transfer rates: we use setlogmask(0) even to decide we don't want to
print debug messages.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 log.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/log.c b/log.c
index 4a70e29..a66ecb7 100644
--- a/log.c
+++ b/log.c
@@ -45,33 +45,33 @@ static time_t	log_start;		/* Start timestamp */
 int		log_trace;		/* --trace mode enabled */
 int		log_to_stdout;		/* Print to stdout instead of stderr */
 
-#define BEFORE_DAEMON		(setlogmask(0) == LOG_MASK(LOG_EMERG))
+#define BEFORE_DAEMON		(log_mask == LOG_MASK(LOG_EMERG))
 
 void vlogmsg(int pri, const char *format, va_list ap)
 {
 	FILE *out = log_to_stdout ? stdout : stderr;
 	struct timespec tp;
 
-	if (setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) {
+	if (log_mask & LOG_MASK(LOG_DEBUG) && log_file == -1) {
 		clock_gettime(CLOCK_REALTIME, &tp);
 		fprintf(out, "%lli.%04lli: ",
 			(long long int)tp.tv_sec - log_start,
 			(long long int)tp.tv_nsec / (100L * 1000));
 	}
 
-	if ((LOG_MASK(LOG_PRI(pri)) & log_mask) || BEFORE_DAEMON) {
+	if ((log_mask & LOG_MASK(LOG_PRI(pri))) || BEFORE_DAEMON) {
 		va_list ap2;
 
 		va_copy(ap2, ap); /* Don't clobber ap, we need it again */
 		if (log_file != -1)
 			logfile_write(pri, format, ap2);
-		else if (!(setlogmask(0) & LOG_MASK(LOG_DEBUG)))
+		else if (!(log_mask & LOG_MASK(LOG_DEBUG)))
 			passt_vsyslog(pri, format, ap2);
 
 		va_end(ap2);
 	}
 
-	if ((setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) ||
+	if ((log_mask & LOG_MASK(LOG_DEBUG) && log_file == -1) ||
 	    (BEFORE_DAEMON && !(log_opt & LOG_PERROR))) {
 		(void)vfprintf(out, format, ap);
 		if (format[strlen(format)] != '\n')
-- 
@@ -45,33 +45,33 @@ static time_t	log_start;		/* Start timestamp */
 int		log_trace;		/* --trace mode enabled */
 int		log_to_stdout;		/* Print to stdout instead of stderr */
 
-#define BEFORE_DAEMON		(setlogmask(0) == LOG_MASK(LOG_EMERG))
+#define BEFORE_DAEMON		(log_mask == LOG_MASK(LOG_EMERG))
 
 void vlogmsg(int pri, const char *format, va_list ap)
 {
 	FILE *out = log_to_stdout ? stdout : stderr;
 	struct timespec tp;
 
-	if (setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) {
+	if (log_mask & LOG_MASK(LOG_DEBUG) && log_file == -1) {
 		clock_gettime(CLOCK_REALTIME, &tp);
 		fprintf(out, "%lli.%04lli: ",
 			(long long int)tp.tv_sec - log_start,
 			(long long int)tp.tv_nsec / (100L * 1000));
 	}
 
-	if ((LOG_MASK(LOG_PRI(pri)) & log_mask) || BEFORE_DAEMON) {
+	if ((log_mask & LOG_MASK(LOG_PRI(pri))) || BEFORE_DAEMON) {
 		va_list ap2;
 
 		va_copy(ap2, ap); /* Don't clobber ap, we need it again */
 		if (log_file != -1)
 			logfile_write(pri, format, ap2);
-		else if (!(setlogmask(0) & LOG_MASK(LOG_DEBUG)))
+		else if (!(log_mask & LOG_MASK(LOG_DEBUG)))
 			passt_vsyslog(pri, format, ap2);
 
 		va_end(ap2);
 	}
 
-	if ((setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) ||
+	if ((log_mask & LOG_MASK(LOG_DEBUG) && log_file == -1) ||
 	    (BEFORE_DAEMON && !(log_opt & LOG_PERROR))) {
 		(void)vfprintf(out, format, ap);
 		if (format[strlen(format)] != '\n')
-- 
2.39.2