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dmeventd_thin: SIGCHLD handler

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To improve reaction time on when child is finished,
lets handle SIGCHLD in particular thread.
Let's hope kernel will route SIGCHLD to matching thread.
This commit is contained in:
Zdenek Kabelac 2017-01-18 09:55:46 +01:00
parent bc7a1d70d4
commit 46c23dfb87
1 changed files with 40 additions and 0 deletions
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40
daemons/dmeventd/plugins/thin/dmeventd_thin.c
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@ -55,6 +55,8 @@ struct dso_state {
uint64_t known_metadata_size;
uint64_t known_data_size;
unsigned fails;
int restore_sigset;
sigset_t old_sigset;
pid_t pid;
char **argv;
char cmd_str[1024];
@ -542,6 +544,41 @@ out:
dm_task_destroy(new_dmt);
}
/* Handle SIGCHLD for a thread */
static void _sig_child(int signum __attribute__((unused)))
{
/* empty SIG_IGN */;
}
/* Setup handler for SIGCHLD when executing external command
* to get quick 'waitpid()' reaction
* It will interrupt syscall just like SIGALRM and
* invoke process_event().
*/
static void _init_thread_signals(struct dso_state *state)
{
struct sigaction act = { .sa_handler = _sig_child };
sigset_t my_sigset;
sigemptyset(&my_sigset);
if (sigaction(SIGCHLD, &act, NULL))
log_warn("WARNING: Failed to set SIGCHLD action.");
else if (sigaddset(&my_sigset, SIGCHLD))
log_warn("WARNING: Failed to add SIGCHLD to set.");
else if (pthread_sigmask(SIG_UNBLOCK, &my_sigset, &state->old_sigset))
log_warn("WARNING: Failed to unblock SIGCHLD.");
else
state->restore_sigset = 1;
}
static void _restore_thread_signals(struct dso_state *state)
{
if (state->restore_sigset &&
pthread_sigmask(SIG_SETMASK, &state->old_sigset, NULL))
log_warn("WARNING: Failed to block SIGCHLD.");
}
int register_device(const char *device,
const char *uuid __attribute__((unused)),
int major __attribute__((unused)),
@ -575,6 +612,7 @@ int register_device(const char *device,
}
dm_split_words(str, maxcmd - 1, 0, state->argv);
_init_thread_signals(state);
}
state->metadata_percent_check = CHECK_MINIMUM;
@ -619,6 +657,8 @@ int unregister_device(const char *device,
if (state->pid != -1)
log_warn("WARNING: Cannot kill child %d!", state->pid);
_restore_thread_signals(state);
dmeventd_lvm2_exit_with_pool(state);
log_info("No longer monitoring thin pool %s.", device);