From 2b86e51026cd39e7c0acc20eceaddc13b67b9977 Mon Sep 17 00:00:00 2001
From: vdahiya12 <67608553+vdahiya12@users.noreply.github.com>
Date: Sun, 19 Jul 2020 20:58:52 -0700
Subject: [PATCH] [daemon_base] fix to not reregister signal handler (#4998)

* [daemon_base] fix to not reregister signal handler

-src/sonic-daemon-base/sonic_daemon_base/daemon_base.py
Problem:
Currently all daemons inherit from daemon_base class, and for
signal handling functionality they register the signal_handler() by
overriding the siganl_handler() in daemon_base by their own
implmentation.
But some sonic_platform instances also can invoke the daemon_base
constructor while trying to instantiate the common utilities
for example
platform_chassis = sonic_platform.platform.Platform().get_chassis()
This will cause the re registration of signal_handler which will
cause base class signal_handler() to be invoked when the daemon
gets a signal, whereas their own signal_handler should have been
invoked.

Fix:
We only register the siganl_handler once, and if signal_handler has
been registered, not re register it.

Signed-off-by: vaibhav-dahiya <vdahiya@microsoft.com>

* [daemon_base] fix to not reregister signal handler

Signed-off-by: vaibhav-dahiya <vdahiya@microsoft.com>
---
 .../sonic_daemon_base/daemon_base.py          | 22 ++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/sonic-daemon-base/sonic_daemon_base/daemon_base.py b/src/sonic-daemon-base/sonic_daemon_base/daemon_base.py
index 205bc9e57f..2debed5227 100644
--- a/src/sonic-daemon-base/sonic_daemon_base/daemon_base.py
+++ b/src/sonic-daemon-base/sonic_daemon_base/daemon_base.py
@@ -96,9 +96,25 @@ class Logger(object):
 class DaemonBase(object):
     def __init__(self):
         # Register our signal handlers
-        signal.signal(signal.SIGHUP, self.signal_handler)
-        signal.signal(signal.SIGINT, self.signal_handler)
-        signal.signal(signal.SIGTERM, self.signal_handler)
+        '''all daemons inherit from daemon_base class, and for
+        signal handling functionality they register the signal_handler() by
+        overriding the siganl_handler() in daemon_base by their own
+        implmentation.
+        But some sonic_platform instances also can invoke the daemon_base
+        constructor while trying to instantiate the common utilities
+        for example
+        platform_chassis = sonic_platform.platform.Platform().get_chassis()
+        This will cause the re registration of signal_handler which will
+        cause base class signal_handler() to be invoked when the daemon
+        gets a signal, whereas the derived class signal_handler should have
+        been invoked. The if checks will not allow the re registration
+        of signal handler '''
+        if not signal.getsignal(signal.SIGHUP):
+            signal.signal(signal.SIGHUP, self.signal_handler)
+        if not signal.getsignal(signal.SIGINT):
+            signal.signal(signal.SIGINT, self.signal_handler)
+        if not signal.getsignal(signal.SIGTERM):
+            signal.signal(signal.SIGTERM, self.signal_handler)
 
     # Signal handler
     def signal_handler(self, sig, frame):