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mdmon: wait for previous mdmon to exit during takeover 

Since the patch c76242c5("mdmon: get safe mode delay file descriptor
early"), safe_mode_dalay is set properly by initrd mdmon.  But in some
cases with filesystem traffic since the very start of the system, it
might take a while to transit to clean state.  Due to fact that new
mdmon does not wait for the old one to exit - it might happen that the
new one switches safe_mode_delay back to seconds, before old one exits.
As the result two mdmons are running concurrently on same array.

Wait for the old mdmon to exit by pinging it with SIGUSR1 signal, just
in case it is sleeping.

Signed-off-by: Pawel Baldysiak <pawel.baldysiak@intel.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>
This commit is contained in:
Pawel Baldysiak 2019-02-22 13:30:27 +01:00 committed by Jes Sorensen
parent 69d084784d
commit d2e11da4b7
1 changed files with 11 additions and 3 deletions
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14
mdmon.c
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@ -171,6 +171,7 @@ static void try_kill_monitor(pid_t pid, char *devname, int sock)
int fd;
int n;
long fl;
int rv;
/* first rule of survival... don't off yourself */
if (pid == getpid())
@ -201,9 +202,16 @@ static void try_kill_monitor(pid_t pid, char *devname, int sock)
fl &= ~O_NONBLOCK;
fcntl(sock, F_SETFL, fl);
n = read(sock, buf, 100);
/* Ignore result, it is just the wait that
* matters
*/
/* If there is I/O going on it might took some time to get to
* clean state. Wait for monitor to exit fully to avoid races.
* Ping it with SIGUSR1 in case that it is sleeping */
for (n = 0; n < 25; n++) {
rv = kill(pid, SIGUSR1);
if (rv < 0)
break;
usleep(200000);
}
}
void remove_pidfile(char *devname)