[systemd-devel] systemd + logind possible deadlock

[Shawn Landden]

meme status

http://gnomememes.tumblr.com/post/48703520110#notes

On Sat, Dec 14, 2013 at 8:56 AM, Zbigniew Jędrzejewski-Szmek
<zbyszek at in.waw.pl> wrote:
> On Sat, Dec 14, 2013 at 11:55:47AM +0200, Oleksii Shevchuk wrote:
>> > strace -p 1
>>
>> stat("/sys", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
>> open("/sys/class/tty/console/active", O_RDONLY|O_CLOEXEC) = 19
>> fstat(19, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fbab0d58000
>> read(19, "ttyS0 tty0\n", 4096)          = 11
>> close(19)                               = 0
>> munmap(0x7fbab0d58000, 4096)            = 0
>> open("/sys/class/tty/tty0/active", O_RDONLY|O_CLOEXEC) = 19
>> fstat(19, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fbab0d58000
>> read(19, "tty7\n", 4096)                = 5
>> close(19)                               = 0
>> munmap(0x7fbab0d58000, 4096)            = 0
>> sendmsg(15, {msg_name(0)=NULL, msg_iov(9)=[{"PRIORITY=6\nSYSLOG_FACILITY=3\nCOD"..., 184}, {"UNIT=SOL.service", 16}, {"\n", 1}, {"MESSAGE_ID=39f53479d3a045ac8e117"..., 43}, {"\n", 1}, {"RESULT=done", 11}, {"\n", 1}, {"MESSAGE=Started SOL.", 20}, {"\n", 1}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL^CProcess 1 detached
>>  <detached ...>
> It's not hangin', just pretendin' :) What y'all think about a little
> patch like this?
>
> -------8<-----------------------------------------------------------
> From 349f5ec587e5e6cc3ad7c89573bb15219eac8920 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek at in.waw.pl>
> Date: Sat, 14 Dec 2013 11:54:26 -0500
> Subject: [PATCH] logging: reduce send timeout to something more sensible
>
> For a user, the timeout of 1 min per message seems equivalent to a hang.
> If journald cannot process a message from PID1 for 10 ms then something
> is significantly wrong. It's better to lose the message and continue.
> ---
>  src/shared/log.c       | 5 ++++-
>  src/shared/time-util.c | 7 +++----
>  2 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/src/shared/log.c b/src/shared/log.c
> index 2404de8..d0616c8 100644
> --- a/src/shared/log.c
> +++ b/src/shared/log.c
> @@ -126,7 +126,10 @@ static int create_log_socket(int type) {
>          /* We need a blocking fd here since we'd otherwise lose
>          messages way too early. However, let's not hang forever in the
>          unlikely case of a deadlock. */
> -        timeval_store(&tv, 1*USEC_PER_MINUTE);
> +        if (getpid() == 1)
> +                timeval_store(&tv, 10 * USEC_PER_MSEC);
> +        else
> +                timeval_store(&tv, 10 * USEC_PER_SEC);
>          setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
>
>          return fd;
> diff --git a/src/shared/time-util.c b/src/shared/time-util.c
> index 55428c4..205fa6f 100644
> --- a/src/shared/time-util.c
> +++ b/src/shared/time-util.c
> @@ -142,12 +142,11 @@ struct timeval *timeval_store(struct timeval *tv, usec_t u) {
>          if (u == (usec_t) -1) {
>                  tv->tv_sec = (time_t) -1;
>                  tv->tv_usec = (suseconds_t) -1;
> -                return tv;
> +        } else {
> +                tv->tv_sec = (time_t) (u / USEC_PER_SEC);
> +                tv->tv_usec = (suseconds_t) (u % USEC_PER_SEC);
>          }
>
> -        tv->tv_sec = (time_t) (u / USEC_PER_SEC);
> -        tv->tv_usec = (suseconds_t) (u % USEC_PER_SEC);
> -
>          return tv;
>  }
>
> --
> 1.8.1.rc0.194.gaf2e3a9
>
> -------8<-----------------------------------------------------------
>
> Zbyszek
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