[Bug,3690] New: fdserver process interferes with signal handling

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State New
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  • [Bug,3690] New: fdserver process interferes with signal handling
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bugzilla-daemon@bugs.linaro.org March 28, 2018, 3:02 p.m.

            Bug ID: 3690
           Summary: fdserver process interferes with signal handling
           Product: OpenDataPlane - linux- generic reference
           Version: master
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: ---
         Component: Shared Memory
          Assignee: christophe.milard@linaro.org
          Reporter: janne.peltonen@nokia.com
                CC: lng-odp@lists.linaro.org
  Target Milestone: ---

The SHM implementation forks a child process that will stay in the same process
group as the parent and will thus receive the signals sent to the group.

One situation where this happens is when an ODP application is run in a shell
and ctrl-C is pressed. An application may set a signal handler to handle ctrl-C
presses in some controlled way, but now there are two problems caused by the

1) The signal handler set by the application runs also in the context of the
fdserver process. The handler may misbehave because the environment in the
fdserver process can be different than in the application controlled processes.

2) Even if the signal handler runs correctly in the fdserver process context,
the main loop of fdserver is not prepared to have its accept() call interrupted
by a signal, causing fdserver to exit.

I bumped into this when wondering about annoying error messages that I got when
stopping the fpm example application of OFP. Problem 1) caused the signal
handler to segfault and if that is fixed in fpm (by doing less in the handler)
then problem 2) would still cause the same error messages.

I am not sure what the right fix would be. Maybe fdserver should do setsid() to
detach itself from the parent's process group, or maybe not because then it
could not output its error messages to the terminal anymore. Or maybe it should
just mask a bunch a signals.

I think fdserver should at least handle EINTR errors so that an application
like fpm can try to handle the rest. This would suffice (some indentation fixes

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diff --git a/platform/linux-generic/_fdserver.c
index 065736f0..af9ca4a0 100644
--- a/platform/linux-generic/_fdserver.c
+++ b/platform/linux-generic/_fdserver.c
@@ -559,8 +559,11 @@  static void wait_requests(int sock)
                addr_sz = sizeof(remote);
                c_socket = accept(sock, (struct sockaddr *)&remote, &addr_sz);
                if (c_socket == -1) {
-                               ODP_ERR("wait_requests: %s\n",
-                               return;
+                       if (errno == EINTR)
+                               continue;
+                       ODP_ERR("wait_requests: %s\n", strerror(errno));
+                       return;