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journald: correctly attribute log messages also with cgroupsv1

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With cgroupsv1 a zombie process is migrated to root cgroup in all
hierarchies. This was changed for unified hierarchy and /proc/PID/cgroup
reports cgroup to which process belonged before it exited.

Be more suspicious about cgroup path reported by the kernel and use
unit_id provided by the log client if the kernel reports that process is
running in the root cgroup.

Users tend to care the most about 'log->unit_id' mapping so systemctl
status can correctly report last log lines. Also we wouldn't be able to
infer anything useful from "/" path anyway.

See: 2e91fa7f6d
This commit is contained in:
Michal Sekletar 2018-12-14 15:17:27 +01:00 committed by Lennart Poettering
parent a9238f6a33
commit 672773b63a
1 changed files with 5 additions and 2 deletions
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7
src/journal/journald-context.c
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@ -14,6 +14,7 @@
#include "journal-util.h"
#include "journald-context.h"
#include "parse-util.h"
#include "path-util.h"
#include "process-util.h"
#include "string-util.h"
#include "syslog-util.h"
@ -252,9 +253,11 @@ static int client_context_read_cgroup(Server *s, ClientContext *c, const char *u
/* Try to acquire the current cgroup path */
r = cg_pid_get_path_shifted(c->pid, s->cgroup_root, &t);
if (r < 0) {
if (r < 0 || empty_or_root(t)) {
/* If that didn't work, we use the unit ID passed in as fallback, if we have nothing cached yet */
/* We use the unit ID passed in as fallback if we have nothing cached yet and cg_pid_get_path_shifted()
* failed or process is running in a root cgroup. Zombie processes are automatically migrated to root cgroup
* on cgroupsv1 and we want to be able to map log messages from them too. */
if (unit_id && !c->unit) {
c->unit = strdup(unit_id);
if (c->unit)