From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Thu, 28 Apr 2022 10:37:56 +0000 (+0000)
Subject: Bug 5208: Part 1: Restart kids killed by SIGKILL (#1035)
X-Git-Tag: SQUID_5_6~3
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=79ff41c6f2cd5c0dbef15929566d3d72da83eb64;p=thirdparty%2Fsquid.git

Bug 5208: Part 1: Restart kids killed by SIGKILL (#1035)

OOM killer uses SIGKILL. Squid did not restart kids killed by SIGKILL.
Kids are essential Squid components. Essential components should be
revived (by default) because providing a service without an essential
component would violate Squid functionality requirements.

Squid did not revive a kid killed by SIGKILL because we thought that
doing so will interfere with the "squid -k kill" feature that uses that
signal to kill the whole Squid instance. However, that feature does not
actually work[^1] -- the signal is sent to (and kills) the master
process only, the process which PID is in squid.pid file. This change is
orthogonal to fixing "squid -k kill" (a difficult out-of-scope project).

[^1]: Except in the special case of the no-daemon (squid -N) mode.
---

diff --git a/src/ipc/Kid.cc b/src/ipc/Kid.cc
index 8c3c7215c0..e2d31dae82 100644
--- a/src/ipc/Kid.cc
+++ b/src/ipc/Kid.cc
@@ -100,7 +100,6 @@ bool Kid::shouldRestart() const
              exitedHappy() ||
              hopeless() ||
              shutting_down ||
-             signaled(SIGKILL) || // squid -k kill
              signaled(SIGINT) || // unexpected forced shutdown
              signaled(SIGTERM)); // unexpected forced shutdown
 }
diff --git a/src/main.cc b/src/main.cc
index a30ba6b3fd..080e71a1a4 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -568,6 +568,7 @@ mainHandleCommandLineOption(const int optId, const char *optValue)
             /** \li On interrupt send SIGINT. */
             opt_send_signal = SIGINT;
         else if (!strncmp(optValue, "kill", strlen(optValue)))
+            // XXX: In SMP mode, uncatchable SIGKILL only kills the master process
             /** \li On kill send SIGKILL. */
             opt_send_signal = SIGKILL;