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journald,core: add short comments we we keep reopening /dev/console all the time

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Just to make sure the next one reading this isn't surprised that the fd isn't
kept open. SAK and stuff...

Fix suggested:

https://github.com/systemd/systemd/pull/4366#issuecomment-253659162
This commit is contained in:
Lennart Poettering 2016-10-19 23:30:50 +02:00
parent e9c880dd2c
commit 8ae2c6300f
2 changed files with 10 additions and 0 deletions
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5
src/core/show-status.c
View file

@ -61,6 +61,11 @@ int status_vprintf(const char *status, bool ellipse, bool ephemeral, const char
if (vasprintf(&s, format, ap) < 0)
return log_oom();
/* Before you ask: yes, on purpose we open/close the console for each status line we write individually. This
* is a good strategy to avoid PID 1 getting killed by the kernel's SAK concept (it doesn't fix this entirely,
* but minimizes the time window the kernel might end up killing PID 1 due to SAK). It also makes things easier
* for us so that we don't have to recover from hangups and suchlike triggered on the console. */
fd = open_terminal("/dev/console", O_WRONLY|O_NOCTTY|O_CLOEXEC);
if (fd < 0)
return fd;

5
src/journal/journald-console.c
View file

@ -102,6 +102,11 @@ void server_forward_console(
tty = s->tty_path ? s->tty_path : "/dev/console";
/* Before you ask: yes, on purpose we open/close the console for each log line we write individually. This is a
* good strategy to avoid journald getting killed by the kernel's SAK concept (it doesn't fix this entirely,
* but minimizes the time window the kernel might end up killing journald due to SAK). It also makes things
* easier for us so that we don't have to recover from hangups and suchlike triggered on the console. */
fd = open_terminal(tty, O_WRONLY|O_NOCTTY|O_CLOEXEC);
if (fd < 0) {
log_debug_errno(fd, "Failed to open %s for logging: %m", tty);