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SubjectRe: [PATCH 13/24] perf daemon: Allow only one daemon over base directory
Em Mon, Feb 08, 2021 at 09:08:57PM +0100, Jiri Olsa escreveu:
> Add 'lock' file under daemon base and flock it, so only one
> perf daemon can run on top of it.
>
> Each daemon tries to create and lock BASE/lock file, if it's
> successful we are sure we're the only daemon running over
> the BASE.
>
> Once daemon is finished, file descriptor to lock file is
> closed and lock is released.
>
> Example:
>
> # cat ~/.perfconfig
> [daemon]
> base=/opt/perfdata
>
> [session-cycles]
> run = -m 10M -e cycles --overwrite --switch-output -a
>
> [session-sched]
> run = -m 20M -e sched:* --overwrite --switch-output -a
>
> Starting the daemon:
>
> # perf daemon start
>
> And try once more:
>
> # perf daemon start
> failed: another perf daemon (pid 775594) owns /opt/perfdata
>
> will end up with an error, because there's already one running
> on top of /opt/perfdata.

Had to add this:

Committer notes:

Provide lockf(F_TLOCK) when not available, i.e. transform:

lockf(fd, F_TLOCK, 0);

into:

flock(fd, LOCK_EX | LOCK_NB);

Which should be equivalent.

Noticed when cross building to some odd Android NDK.

------

Patch:

[acme@five perf]$ git diff
diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c
index 1c17c9e10ca6a656..2890573540f7d027 100644
--- a/tools/perf/builtin-daemon.c
+++ b/tools/perf/builtin-daemon.c
@@ -914,6 +914,20 @@ static int setup_config(struct daemon *daemon)
return daemon->config_real ? 0 : -1;
}

+#ifndef F_TLOCK
+#define F_TLOCK 2
+
+#include <sys/file.h>
+
+static int lockf(int fd, int cmd, off_t len)
+{
+ if (cmd != F_TLOCK || len != 0)
+ return -1;
+
+ return flock(fd, LOCK_EX | LOCK_NB);
+}
+#endif // F_TLOCK
+
/*
* Each daemon tries to create and lock BASE/lock file,
* if it's successful we are sure we're the only daemon
[acme@five perf]$
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