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[daemon_base] fix to not reregister signal handler (#4998)

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* [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>
This commit is contained in:
vdahiya12 2020-07-19 20:58:52 -07:00 committed by GitHub
parent aa9e1e2f43
commit c9983df062
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1 changed files with 19 additions and 3 deletions
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src/sonic-daemon-base/sonic_daemon_base/daemon_base.py
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@ -90,9 +90,25 @@ 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):