From 983464ffad11a0f8c5656492f3c342139acd2527 Mon Sep 17 00:00:00 2001

From: Liu Hua <weldonliu@tencent.com>

Date: Thu, 4 Nov 2021 10:04:22 +0800

Subject: [PATCH 052/120] crtools: ignore SIGPIPE in swrk mode

Criu ignores SIGPIPE in most cases except swrk mode. And in the

following situtation criu get killed by SIGPIPE and have no chance

to do cleanup: Connection to page server is lost when we do disk-less

migration, criu send PS_IOV_FLUSH via a broken connction in

disconnect_from_page_server.

This patch let criu ignore SIGPIPE in all paths .

Signed-off-by: Liu Hua <weldonliu@tencent.com>

---

 criu/crtools.c | 33 ++++++++++++++++++---------------

 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/criu/crtools.c b/criu/crtools.c

index 6a75cd1ea..81c0aa963 100644

--- a/criu/crtools.c

+++ b/criu/crtools.c

@@ -106,6 +106,24 @@ int main(int argc, char *argv[], char *envp[])

 	log_set_loglevel(opts.log_level);

+	/*

+	 * There kernel might send us lethal signals in the following cases:

+	 * 1) Writing a pipe which reader has disappeared.

+	 * 2) Writing to a socket of type SOCK_STREAM which is no longer connected.

+	 * We deal with write()/Send() failures on our own, and prefer not to get killed.

+	 * So we ignore SIGPIPEs.

+	 *

+	 * Pipes are used in various places:

+	 * 1) Receiving application page data

+	 * 2) Transmitting data to the image streamer

+	 * 3) Emitting logs (potentially to a pipe).

+	 * Sockets are mainly used in transmitting memory data.

+	 */

+	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) {

+		pr_perror("Failed to set a SIGPIPE signal ignore.");

+		return 1;

+	}

+

 	if (optind < argc && !strcmp(argv[optind], "swrk")) {

 		if (argc != optind + 2) {

 			fprintf(stderr, "Usage: criu swrk <fd>\n");

@@ -175,21 +193,6 @@ int main(int argc, char *argv[], char *envp[])

 		}

 	}

-	/*

-	 * The kernel might send us lethal signals when writing to a pipe

-	 * which reader has disappeared. We deal with write() failures on our

-	 * own, and prefer not to get killed. So we ignore SIGPIPEs.

-	 *

-	 * Pipes are used in various places:

-	 * 1) Receiving application page data

-	 * 2) Transmitting data to the image streamer

-	 * 3) Emitting logs (potentially to a pipe).

-	 */

-	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) {

-		pr_perror("Failed to set a SIGPIPE signal ignore.");

-		return 1;

-	}

-

 	/*

 	 * When a process group becomes an orphan,

 	 * its processes are sent a SIGHUP signal

-- 

2.34.1