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From: Martin Wilck <mwilck@suse.com>
To: Bart Van Assche <Bart.VanAssche@wdc.com>,
	"bmarzins@redhat.com" <bmarzins@redhat.com>
Cc: "dm-devel@redhat.com" <dm-devel@redhat.com>
Subject: Re: [PATCH] multipathd: fix inverted signal blocking logic
Date: Mon, 05 Mar 2018 18:28:05 +0100	[thread overview]
Message-ID: <1520270885.7660.36.camel@suse.com> (raw)
In-Reply-To: <1520267239.2826.17.camel@wdc.com>

Hello Bart,

On Mon, 2018-03-05 at 16:27 +0000, Bart Van Assche wrote:
> On Sat, 2018-03-03 at 01:31 +0100, Martin Wilck wrote:
> > So, there's no reason not to block them, right? Is it expected
> > behavior
> > that a user running 'kill -USR2 $(pidof multipathd)' terminates the
> > process? Why do you think these signals should interrupt ppoll()
> > although the uxlsnr can't can't handle them? Isn't it sufficient
> > that
> > they're handled by the threads that are meant to do that?
> 
> Blocking all signals except the ones for which we installed a handler
> sounds
> weird to me. I think users expect daemons to process signals instead
> of
> blocking all but a specific set of signals. This is a rather
> philosophical
> argument and not an argument of which I think that it is strong
> enough to
> prevent this patch of being integrated in the upstream multipath-
> tools
> repository.

Thank you. Meanwhile, I found that this patch requires a change in the
"marginal paths" code. I'll post an official patch as update.

Regarding the philosophical discussion, may I remind you of your own
words from 534ec4c?

    The POSIX standard mentions that the only way to guarantee that
    signals are delivered to a specific thread is:
     * Block all signals before the first pthread_create() call.
     * Unblock signals from the thread that should receive signals.

If we unblock signals with a default disposition of "Term" for which we
have no handler, stray signals caught would terminate multipathd. I
don't think that's what we want. Of course we must react on
SIGINT/SIGTERM/SIGHUP in the way the user expects us to, but
terminating on other signals would be wrong.

Let's see if others have to say anything about this.

Martin

-- 
Dr. Martin Wilck <mwilck@suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)

--
dm-devel mailing list
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https://www.redhat.com/mailman/listinfo/dm-devel

  reply	other threads:[~2018-03-05 17:28 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-20 13:26 [RFC PATCH 00/20] "Foreign" NVMe support for multipath-tools Martin Wilck
2018-02-20 13:26 ` [RFC PATCH 01/20] multipath(d)/Makefile: add explicit dependency on libraries Martin Wilck
2018-03-01  5:35   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 02/20] libmultipath: remove unused "stdout helpers" Martin Wilck
2018-03-01  5:36   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 03/20] libmultipath: get rid of selector "hack" in print.c Martin Wilck
2018-03-01  5:36   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 04/20] libmultipath: parser: use call-by-value for "snprint" methods Martin Wilck
2018-03-01  5:37   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 05/20] libmultipath: don't update path groups when printing Martin Wilck
2018-02-28 23:40   ` Benjamin Marzinski
2018-03-02 13:59     ` Martin Wilck
2018-03-02 15:31       ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 06/20] libmultipath/print: use "const" where appropriate Martin Wilck
2018-03-01  5:37   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 07/20] libmultipath: use "const" in devmapper code Martin Wilck
2018-03-01  5:39   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 08/20] libmultipath: fix compiler warnings for -Wcast-qual Martin Wilck
2018-03-01  5:39   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 09/20] multipath-tools: Makefile.inc: use -Werror=cast-qual Martin Wilck
2018-03-01  5:59   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 10/20] libmultipath: add vector_free_const() Martin Wilck
2018-03-01  6:00   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 11/20] libmultipath: add vector_convert() Martin Wilck
2018-03-01  6:02   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 12/20] libmultipath: "generic multipath" interface Martin Wilck
2018-02-28 23:47   ` Benjamin Marzinski
2018-03-01  8:51     ` Martin Wilck
2018-02-20 13:26 ` [RFC PATCH 13/20] libmultipath: print: convert API to generic data type Martin Wilck
2018-02-28 23:55   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 14/20] libmultipath: print: use generic API for get_x_layout() Martin Wilck
2018-03-01  6:03   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 15/20] libmultipath: API for foreign multipath handling Martin Wilck
2018-03-01  3:01   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 16/20] libmultipath/print: add "%G - foreign" wildcard Martin Wilck
2018-03-01  6:04   ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 17/20] libmultipath/foreign: nvme foreign library Martin Wilck
2018-03-01  3:14   ` Benjamin Marzinski
2018-03-02 16:04     ` Martin Wilck
2018-03-02 18:30       ` Benjamin Marzinski
2018-02-20 13:26 ` [RFC PATCH 18/20] multipath: use foreign API Martin Wilck
2018-03-01  3:55   ` Benjamin Marzinski
2018-03-02 16:36     ` Martin Wilck
2018-02-20 13:26 ` [RFC PATCH 19/20] multipathd: " Martin Wilck
2018-03-01  5:13   ` Benjamin Marzinski
2018-03-02 17:04     ` Martin Wilck
2018-03-02 18:42       ` Benjamin Marzinski
2018-03-02 19:19     ` Martin Wilck
2018-03-02 20:00       ` Benjamin Marzinski
2018-03-02 21:18         ` [PATCH] multipathd: fix inverted signal blocking logic Martin Wilck
2018-03-02 21:35           ` Bart Van Assche
2018-03-02 22:15             ` Martin Wilck
2018-03-02 22:23               ` Bart Van Assche
2018-03-02 23:16                 ` Martin Wilck
2018-03-02 23:27                   ` Bart Van Assche
2018-03-03  0:31                     ` Martin Wilck
2018-03-05 16:27                       ` Bart Van Assche
2018-03-05 17:28                         ` Martin Wilck [this message]
2018-03-06  0:46                           ` Benjamin Marzinski
2018-03-06  8:48                             ` Martin Wilck
2018-03-02 21:00     ` [RFC PATCH 19/20] multipathd: use foreign API Bart Van Assche
2018-02-20 13:26 ` [RFC PATCH 20/20] libmultipath: foreign/nvme: implement path display Martin Wilck
2018-03-01  5:19   ` Benjamin Marzinski

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