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From: Benjamin Marzinski <bmarzins@redhat.com>
To: mwilck@suse.com
Cc: lixiaokeng@huawei.com, dm-devel@redhat.com
Subject: Re: [dm-devel] [PATCH v2 01/29] multipathd: uxlsnr: avoid deadlock on exit
Date: Tue, 20 Oct 2020 14:04:55 -0500
Message-ID: <20201020190455.GO3384@octiron.msp.redhat.com> (raw)
In-Reply-To: <20201016104501.8700-2-mwilck@suse.com>

On Fri, Oct 16, 2020 at 12:44:33PM +0200, mwilck@suse.com wrote:
> From: Martin Wilck <mwilck@suse.com>
> 
> The uxlsnr wouldn't always release the client lock when cancelled,
> causing a deadlock in uxsock_cleanup(). While this hasn't been
> caused by commit 3d611a2, the deadlock seems to have become much
> more likely after that patch. Solving this means that we have to
> treat reallocation failure of the pollfd array differently.
> We will now just ignore any clients above the last valid pfd index.
> That's a minor problem, as we're in an OOM situation anyway.
> 
> Moreover, client_lock is not a "struct lock", but a plain
> pthread_mutex_t.
> 
> Fixes: 3d611a2 ("multipathd: cancel threads early during shutdown")

Oops. Forgot to send this one.

Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> ---
>  multipathd/uxlsnr.c | 24 ++++++++++++++----------
>  1 file changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/multipathd/uxlsnr.c b/multipathd/uxlsnr.c
> index 1c5ce9d..ce2b680 100644
> --- a/multipathd/uxlsnr.c
> +++ b/multipathd/uxlsnr.c
> @@ -35,6 +35,7 @@
>  #include "config.h"
>  #include "mpath_cmd.h"
>  #include "time-util.h"
> +#include "util.h"
>  
>  #include "main.h"
>  #include "cli.h"
> @@ -116,7 +117,7 @@ static void _dead_client(struct client *c)
>  
>  static void dead_client(struct client *c)
>  {
> -	pthread_cleanup_push(cleanup_lock, &client_lock);
> +	pthread_cleanup_push(cleanup_mutex, &client_lock);
>  	pthread_mutex_lock(&client_lock);
>  	_dead_client(c);
>  	pthread_cleanup_pop(1);
> @@ -302,10 +303,11 @@ void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
>  	sigdelset(&mask, SIGUSR1);
>  	while (1) {
>  		struct client *c, *tmp;
> -		int i, poll_count, num_clients;
> +		int i, n_pfds, poll_count, num_clients;
>  
>  		/* setup for a poll */
>  		pthread_mutex_lock(&client_lock);
> +		pthread_cleanup_push(cleanup_mutex, &client_lock);
>  		num_clients = 0;
>  		list_for_each_entry(c, &clients, node) {
>  			num_clients++;
> @@ -322,14 +324,13 @@ void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
>  						sizeof(struct pollfd));
>  			}
>  			if (!new) {
> -				pthread_mutex_unlock(&client_lock);
>  				condlog(0, "%s: failed to realloc %d poll fds",
>  					"uxsock", 2 + num_clients);
> -				sched_yield();
> -				continue;
> +				num_clients = old_clients;
> +			} else {
> +				old_clients = num_clients;
> +				polls = new;
>  			}
> -			old_clients = num_clients;
> -			polls = new;
>  		}
>  		polls[0].fd = ux_sock;
>  		polls[0].events = POLLIN;
> @@ -347,11 +348,14 @@ void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
>  			polls[i].fd = c->fd;
>  			polls[i].events = POLLIN;
>  			i++;
> +			if (i >= 2 + num_clients)
> +				break;
>  		}
> -		pthread_mutex_unlock(&client_lock);
> +		n_pfds = i;
> +		pthread_cleanup_pop(1);
>  
>  		/* most of our life is spent in this call */
> -		poll_count = ppoll(polls, i, &sleep_time, &mask);
> +		poll_count = ppoll(polls, n_pfds, &sleep_time, &mask);
>  
>  		handle_signals(false);
>  		if (poll_count == -1) {
> @@ -384,7 +388,7 @@ void * uxsock_listen(uxsock_trigger_fn uxsock_trigger, long ux_sock,
>  		}
>  
>  		/* see if a client wants to speak to us */
> -		for (i = 2; i < num_clients + 2; i++) {
> +		for (i = 2; i < n_pfds; i++) {
>  			if (polls[i].revents & POLLIN) {
>  				struct timespec start_time;
>  
> -- 
> 2.28.0

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Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-16 10:44 [dm-devel] [PATCH v2 00/29] libmultipath: improve cleanup " mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 01/29] multipathd: uxlsnr: avoid deadlock " mwilck
2020-10-20 19:04   ` Benjamin Marzinski [this message]
2020-10-16 10:44 ` [dm-devel] [PATCH v2 02/29] multipathd: Fix liburcu memory leak mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 03/29] multipathd: move handling of io_err_stat_attr into libmultipath mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 04/29] multipathd: move vecs desctruction into cleanup function mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 05/29] multipathd: make some globals static mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 06/29] multipathd: move threads destruction into separate function mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 07/29] multipathd: move conf " mwilck
2020-10-19 18:56   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 08/29] multipathd: move pid " mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 09/29] multipathd: close pidfile on exit mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 10/29] multipathd: add helper for systemd notification at exit mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 11/29] multipathd: child(): call cleanups in failure case, too mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 12/29] multipathd: unwatch_all_dmevents: check if waiter is initialized mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 13/29] multipathd: print error message if config can't be loaded mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 14/29] libmultipath: add libmp_dm_exit() mwilck
2020-10-19 19:07   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 15/29] multipathd: fixup libdm deinitialization mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 16/29] libmultipath: log_thread_stop(): check if logarea is initialized mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 17/29] multipathd: add cleanup_child() exit handler mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 18/29] libmultipath: fix log_thread startup and teardown mwilck
2020-10-19 20:00   ` Benjamin Marzinski
2020-10-26 13:58     ` Martin Wilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 19/29] multipathd: move cleanup_{prio, checkers, foreign} to libmultipath_exit mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 20/29] multipath: use atexit() for cleanup handlers mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 21/29] mpathpersist: " mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 22/29] multipath: fix leaks in check_path_valid() mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 23/29] multipath-tools: mpath-tools.supp: file with valgrind suppressions mwilck
2020-10-19 20:01   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 24/29] libmultipath: use libmp_verbosity to track verbosity mwilck
2020-10-19 20:38   ` Benjamin Marzinski
2020-10-26 14:47     ` Martin Wilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 25/29] libmultipath: introduce symbolic values for logsink mwilck
2020-10-16 20:13   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 26/29] libmultipath: simplify dlog() mwilck
2020-10-19 21:07   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 27/29] multipathd: common code for "-k" and command args mwilck
2020-10-19 21:51   ` Benjamin Marzinski
2020-10-16 10:45 ` [dm-devel] [PATCH v2 28/29] multipathd: sanitize uxsock_listen() mwilck
2020-10-19 23:33   ` Benjamin Marzinski
2020-10-26 13:54     ` Martin Wilck
2020-10-16 10:45 ` [dm-devel] [PATCH v2 29/29] libmultipath: fix race between log_safe and log_thread_stop() mwilck
2020-10-20  2:20   ` Benjamin Marzinski
2020-10-26 16:22     ` Martin Wilck
2020-10-26 17:24       ` Martin Wilck
2020-11-03  0:11         ` Benjamin Marzinski
2020-11-04 12:36           ` Martin Wilck
2020-11-04 15:46             ` Benjamin Marzinski

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