Re: [libvirt] [PATCH] util: ignore SIGPIPE when writing tostderr/stdout
On Sat, Oct 12, 2019 at 04:04:11PM +0800, Wang Yechao wrote:
> libvirtd's stderr/stdout redirected to journald by default, so if
> the journald has stopped, libvirtd and libvirtd's child process
> will receive SIGPIPE signal when writing logs to stderr/stdout.
>
> journald stopped reasons:
> 1. manual command "systemctl stop systemd-journald.service"
Don't do that then IMHO.
I just do it to reproduce this scenes.
> 2. oom killer kill it.
> ...
If OOM killer picked journald, then it is game over for the host IMHO
and thed right answer is a reboot. This would be very surprising though.
OOM killer is more likely to pick QEMU or libvirtd as they're bigger
targets.
Reboot is the best way. But sometimes, the oom is caused by a abnormal process,
if we stop it, the system's free memory will back to normal. And i think it's
no need to reboot.
>
> Signed-off-by: Wang Yechao <wang.yechao255(a)zte.com.cn>
> ---
> src/util/virlog.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/src/util/virlog.c b/src/util/virlog.c
> index 4c76fbc..127e121 100644
> --- a/src/util/virlog.c
> +++ b/src/util/virlog.c
> @@ -39,6 +39,7 @@
> # include <sys/un.h>
> #endif
> #include <fnmatch.h>
> +#include <signal.h>
>
> #include "virerror.h"
> #include "virlog.h"
> @@ -732,6 +733,9 @@ virLogOutputToFd(virLogSourcePtr source ATTRIBUTE_UNUSED,
> if (fd < 0)
> return;
>
> + if (fd == STDERR_FILENO || fd == STDOUT_FILENO)
> + signal(SIGPIPE, SIG_IGN);
This is very wrong....
This code is run in both client & server, so we're messing with SIGPIPE
in applications that link to libvirt.so.
Thanks to point my fault.
The use of signal() is not safe in multi-threaded applications.
In libvirtd we have set SIGPIPE to ignored already when starting up
libvirtd.
Can set SIGPIPE to ignored in the child process that forked by libvirtd ?
---
Best wishes
Wang Yechao