[PATCH] Use sigaction and SA_RESTART in read-tree.c; add option in Makefile.

[Jason Riedy <ejr@EECS.Berkeley.EDU>]

Might as well ape the sigaction change in read-tree.c to avoid
the same potential problems.  The fprintf status output will
be overwritten in a second, so don't bother guarding it.  Do
move the fputc after disabling SIGALRM to ensure we go to the
next line, though.

Also add a NO_SA_RESTART option in the Makefile in case someone
doesn't have SA_RESTART but does restart (maybe older HP/UX?).
We want the builder to chose this specifically in case the
system both lacks SA_RESTART and does not restart stdio calls;
a compat #define in git-compat-utils.h would silently allow
broken systems.

Signed-off-by: Jason Riedy <ejr@cs.berkeley.edu>

---

 Makefile    |    7 +++++++
 read-tree.c |   28 +++++++++++++++++++---------
 2 files changed, 26 insertions(+), 9 deletions(-)

521dc260ea90a23d58a4e920203af5035ca1a673
diff --git a/Makefile b/Makefile
index c79d646..f3b1d49 100644
--- a/Makefile
+++ b/Makefile
@@ -63,6 +63,9 @@
 # Define COLLISION_CHECK below if you believe that SHA1's
 # 1461501637330902918203684832716283019655932542976 hashes do not give you
 # sufficient guarantee that no collisions between objects will ever happen.
+#
+# Define NO_SA_RESTART if your platform does not have SA_RESTART, _AND_ if
+# it automatically restarts interrupted stdio calls.
 
 # Define USE_NSEC below if you want git to care about sub-second file mtimes
 # and ctimes. Note that you need recent glibc (at least 2.2.4) for this, and
@@ -425,6 +428,10 @@
 endif
 ifdef NO_ACCURATE_DIFF
 	ALL_CFLAGS += -DNO_ACCURATE_DIFF
+endif
+
+ifdef NO_SA_RESTART
+	ALL_CFLAGS += -DSA_RESTART=0
 endif
 
 # Shell quote (do not use $(call) to accomodate ancient setups);
diff --git a/read-tree.c b/read-tree.c
index eaff444..4422dbf 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -273,10 +273,26 @@
 
 static void progress_interval(int signum)
 {
-	signal(SIGALRM, progress_interval);
 	progress_update = 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);
+}
+
 static void check_updates(struct cache_entry **src, int nr)
 {
 	static struct checkout state = {
@@ -289,8 +305,6 @@
 	unsigned last_percent = 200, cnt = 0, total = 0;
 
 	if (update && verbose_update) {
-		struct itimerval v;
-
 		for (total = cnt = 0; cnt < nr; cnt++) {
 			struct cache_entry *ce = src[cnt];
 			if (!ce->ce_mode || ce->ce_flags & mask)
@@ -302,12 +316,8 @@
 			total = 0;
 
 		if (total) {
-			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, "Checking files out...\n");
+			setup_progress_signal();
 			progress_update = 1;
 		}
 		cnt = 0;
@@ -341,8 +351,8 @@
 		}
 	}
 	if (total) {
-		fputc('\n', stderr);
 		signal(SIGALRM, SIG_IGN);
+		fputc('\n', stderr);
 	}
 }
 
-- 
1.3.0.rc1