[stgt] [PATCH] fixes in call_program (closing pipe fds, waitpid interrupted by a signal)

[Alexander Nezhinsky]

Some fixes in call_program():
1) if fork() fails, previously open pipe file descriptors should be closed.
2) the redirect script is invoked from a fork'ed process so tgt has to wait
for its child. Currently this is done synchronously using waitpid().
Sometimes the system call is interrupted by a signal (most probably by
a SIGCHLD signal from the very process that is being waited upon).
To overcome this, waitpid() is called repeatedly while the error code
is "Interrupted by a signal". Other reasons for failure are non-existing
process or invalid arguments, so in these cases we shall just give up.

Signed-off-by: Alexander Nezhinsky <alexandern at voltaire.com>
---
 usr/tgtd.c |   32 +++++++++++++++++++++++++-------
 1 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/usr/tgtd.c b/usr/tgtd.c
index c3abca8..066f46e 100644
--- a/usr/tgtd.c
+++ b/usr/tgtd.c
@@ -285,27 +285,45 @@ int call_program(const char *cmd, void (*callback)(void *data, int result),
 	argv[i] =  NULL;
 
 	ret = pipe(fds);
-	if (ret < 0)
+	if (ret < 0) {
+		eprintf("pipe create failed for %s, %m\n", cmd);
 		return ret;
+	}
 
-	eprintf("%d %d\n", fds[0], fds[1]);
+	dprintf("%s, pipe: %d %d\n", cmd, fds[0], fds[1]);
 
 	pid = fork();
-	if (pid < 0)
+	if (pid < 0) {
+		eprintf("fork failed for: %s, %m\n", cmd);
+		close(fds[0]);
+		close(fds[1]);
 		return pid;
+	}
 
 	if (!pid) {
 		close(1);
 		dup(fds[1]);
 		close(fds[0]);
-		ret = execv(argv[0], argv);
+		execv(argv[0], argv);
+
+		eprintf("execv failed for: %s, %m\n", cmd);
 		exit(-1);
 	} else {
 		close(fds[1]);
-		waitpid(pid, &i, 0);
+		do {
+			ret = waitpid(pid, &i, 0);
+		} while (ret < 0 && errno == EINTR);
+		if (ret < 0) {
+			eprintf("waitpid failed for: %s, %m\n", cmd);
+			close(fds[0]);
+			return ret;
+		}
 		ret = read(fds[0], output, op_len);
-		if (ret < 0)
-			eprintf("failed to get the output from <%s>.", cmd);
+		if (ret < 0) {
+			eprintf("failed to get the output from: %s\n", cmd);
+			close(fds[0]);
+			return ret;
+		}
 
 		if (callback)
 			callback(data, WEXITSTATUS(i));
--
1.6.5.5
--
To unsubscribe from this list: send the line "unsubscribe stgt" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html