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libdaemon: use pselect to avoid condition checking race

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To avoid tiny race on checking arrival of signal and entering select
(that can latter remain stuck as signal was already delivered) switch
to use  pselect().

If it would needed, we can eventually add extra code for older systems
without pselect(), but there are probably no such ancient systems in
use.
This commit is contained in:
Zdenek Kabelac 2019-04-10 12:50:53 +02:00
parent 116bd314cb
commit 44cfa55843
4 changed files with 31 additions and 12 deletions
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1
WHATS_NEW
View File

@ -1,5 +1,6 @@
Version 2.03.02 -
===================================
Fix signal delivery checking race in libdaemon (lvmetad).
Add missing Before=shutdown.target to LVM2 services to fix shutdown ordering.
Skip autoactivation for a PV when PV size does not match device size.
Remove first-pvscan-initialization which should no longer be needed.

2
daemons/lvmpolld/lvmpolld-core.c
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@ -915,7 +915,7 @@ int main(int argc, char *argv[])
int option_index = 0;
int client = 0, server = 0;
unsigned action = ACTION_MAX;
struct timeval timeout;
struct timespec timeout;
daemon_idle di = { .ptimeout = &timeout };
struct lvmpolld_state ls = { .log_config = "" };
daemon_state s = {

36
libdaemon/server/daemon-server.c
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@ -85,7 +85,7 @@ static int _is_idle(daemon_state s)
return s.idle && s.idle->is_idle && !s.threads->next;
}
static struct timeval *_get_timeout(daemon_state s)
static struct timespec *_get_timeout(daemon_state s)
{
return s.idle ? s.idle->ptimeout : NULL;
}
@ -94,7 +94,7 @@ static void _reset_timeout(daemon_state s)
{
if (s.idle) {
s.idle->ptimeout->tv_sec = 1;
s.idle->ptimeout->tv_usec = 0;
s.idle->ptimeout->tv_nsec = 0;
}
}
@ -559,6 +559,8 @@ void daemon_start(daemon_state s)
thread_state _threads = { .next = NULL };
unsigned timeout_count = 0;
fd_set in;
sigset_t new_set, old_set;
int ret;
/*
* Switch to C locale to avoid reading large locale-archive file used by
@ -626,8 +628,7 @@ void daemon_start(daemon_state s)
if (!s.foreground)
kill(getppid(), SIGTERM);
/*
* Use daemon_main for daemon-specific init and polling, or
/* * Use daemon_main for daemon-specific init and polling, or
* use daemon_init for daemon-specific init and generic lib polling.
*/
@ -641,22 +642,39 @@ void daemon_start(daemon_state s)
if (!s.daemon_init(&s))
failed = 1;
if (s.socket_fd >= FD_SETSIZE)
failed = 1; /* FD out of available selectable set */
sigfillset(&new_set);
sigprocmask(SIG_SETMASK, NULL, &old_set);
while (!failed) {
_reset_timeout(s);
FD_ZERO(&in);
FD_SET(s.socket_fd, &in);
if (select(FD_SETSIZE, &in, NULL, NULL, _get_timeout(s)) < 0 && errno != EINTR)
sigprocmask(SIG_SETMASK, &new_set, NULL);
if (_shutdown_requested && !s.threads->next) {
sigprocmask(SIG_SETMASK, &old_set, NULL);
INFO(&s, "shutdown requested", s.name);
break;
}
ret = pselect(s.socket_fd + 1, &in, NULL, NULL, _get_timeout(s), &old_set);
sigprocmask(SIG_SETMASK, &old_set, NULL);
if (ret < 0) {
if (errno != EINTR && errno != EAGAIN &&
(EWOULDBLOCK == EAGAIN || errno != EWOULDBLOCK))
perror("select error");
continue;
}
if (FD_ISSET(s.socket_fd, &in)) {
timeout_count = 0;
_handle_connect(s);
}
_reap(s, 0);
if (_shutdown_requested && !s.threads->next)
break;
/* s.idle == NULL equals no shutdown on timeout */
if (_is_idle(s)) {
DEBUGLOG(&s, "timeout occured");

2
libdaemon/server/daemon-server.h
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@ -47,7 +47,7 @@ struct timeval;
typedef struct {
volatile unsigned is_idle;
unsigned max_timeouts;
struct timeval *ptimeout;
struct timespec *ptimeout;
} daemon_idle;
struct daemon_state;