Re: Solaris cloning woes partly diagnosed

From: Linus Torvalds <torvalds@osdl.org>
Date: Apr 2, 2006, 20:28 UTC
Message-ID: <Pine.LNX.4.64.0604021312510.3050@g5.osdl.org>
In-Reply-To: <824.1144007555@lotus.CS.Berkeley.EDU>

On Sun, 2 Apr 2006, Jason Riedy wrote:

> 
> Solaris folks will say you should be using sigaction with
> SA_RESTART.  IIRC, SA_RESTART isn't guaranteed to be there 
> or work, but all the systems I deal with right now have it.

I think we might as well do that _too_.

However, once you use "sigaction()", you don't need to re-arm the signal handler any more, so I'd suggest a simpler patch like this instead..

Junio, I think this confirms/explains the Solaris breakage.

I'll re-send the "anal stdio semantics" version of the patch on top of this in the next email.

			Linus
----
Subject: Fix Solaris stdio signal handling stupidities

This uses sigaction() to install the SIGALRM handler with SA_RESTART, so that Solaris stdio doesn't break completely when a signal interrupts a read.

Thanks to Jason Riedy for confirming the silly Solaris signal behaviour.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
----

diff --git a/pack-objects.c b/pack-objects.c
index ccfaa5f..1817b58 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -58,7 +58,7 @@ static int nr_objects = 0, nr_alloc = 0,
 static const char *base_name;
 static unsigned char pack_file_sha1[20];
 static int progress = 1;
-static volatile int progress_update = 0;
+static volatile sig_atomic_t progress_update = 0;
 
 /*
  * The object names in objects array are hashed with this hashtable,
@@ -879,7 +879,6 @@ static int try_delta(struct unpacked *cu
 
 static void progress_interval(int signum)
 {
-	signal(SIGALRM, progress_interval);
 	progress_update = 1;
 }
 
@@ -1025,6 +1024,23 @@ static int reuse_cached_pack(unsigned ch
 	return 1;
 }
 
+static void setup_progress_signal(void)
+{
+	struct sigaction sa;
+	struct itimerval v;
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = progress_interval;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = SA_RESTART;
+	sigaction(SIGALRM, &sa, NULL);
+
+	v.it_interval.tv_sec = 1;
+	v.it_interval.tv_usec = 0;
+	v.it_value = v.it_interval;
+	setitimer(ITIMER_REAL, &v, NULL);
+}
+
 int main(int argc, char **argv)
 {
 	SHA_CTX ctx;
@@ -1090,13 +1106,8 @@ int main(int argc, char **argv)
 	prepare_packed_git();
 
 	if (progress) {
-		struct itimerval v;
-		v.it_interval.tv_sec = 1;
-		v.it_interval.tv_usec = 0;
-		v.it_value = v.it_interval;
-		signal(SIGALRM, progress_interval);
-		setitimer(ITIMER_REAL, &v, NULL);
 		fprintf(stderr, "Generating pack...\n");
+		setup_progress_signal();
 	}
 
 	while (fgets(line, sizeof(line), stdin) != NULL) {