On Sun, Jun 29, 2014 at 08:37:25PM -0700, Ansis Atteka wrote:
> From: Ansis <ansisatt...@gmail.com>
Fix up the patch author?
> The child process (the one being monitored) could die before it was able
> to call fork_notify_startup() function. If such situation arises, then
> parent process (the one monitoring child process) would also terminate
> with a fatal log message:
>
> ...|EMER|fork child died before signaling startup (killed (...))
>
> This patch changes that beahvior by always restarting child process
> if it was able to start up at least once in the past. However, if
> child was not able to start up even the first time, then monitor process
> would still terminate, because that would most likely indicate a
> persistent programming error.
>
> To reproduce use following script:
>
> while : ; do kill -SIGSEGV `cat /var/run/openvswitch/ovs-vswitchd.pid`; done
>
> Signed-Off-By: Ansis Atteka <aatt...@nicira.com>
> Issue: 1273550
Clang does not like this:
../lib/daemon-unix.c:338:13: error: variable 'retval' is used uninitialized
whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
if (child_ready) {
^~~~~~~~~~~
../lib/daemon-unix.c:347:13: note: uninitialized use occurs here
if (retval == daemon_pid || !child_ready) {
^~~~~~
../lib/daemon-unix.c:338:9: note: remove the 'if' if its condition is always
true
if (child_ready) {
^~~~~~~~~~~~~~~~~
../lib/daemon-unix.c:332:19: note: initialize the variable 'retval' to
silence
this warning
int retval;
^
= 0
1 error generated.
I can kind of see its point. This use of uninitialized data will
never be a real problem, because !child_ready will always be true if
retval is uninitialized, but it still reads better (and pleases Clang)
if the test condition is reversed:
if (!child_ready || retval == daemon_pid) {
I think that the previous code logged something at VLL_EMER level if
the monitor process exited. I think the new version does not; it
would be nice if it did. You might use VLOG_FATAL instead of exit(1)
to get that effect.
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