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From:   Gal Ben Haim <gbenhaim@augury.com>
Date:   Fri, 16 Nov 2018 21:54:48 +0200
Message-ID: <CAHotPr8prG8vfmOeFYD+5rq7U9MtnHDjkhET4M4dwMn4OE-Vug@mail.gmail.com>
Subject: Re: [PATCH BlueZ] core: Ignore SIGPIPE
To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     linux-bluetooth@vger.kernel.org
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there's a suggestion in the thread about my other patch that uses poll
that the signal should be ignored anyway,
to prevent a scenario that the peer disconnects between poll or
checking for MSG_NOSIGNAL and the write attempt.
On Fri, Nov 16, 2018 at 9:30 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi Gal,
>
> On Fri, Nov 16, 2018 at 9:17 PM Gal Ben-Haim <gbenhaim@augury.com> wrote:
> >
> > bluetoothd receives a SIGPIPE and terminates if writing to a pipe that
> > was acquired by AcquireNotify and there are no readers. it can be
> > reproduced by terminating the reader process without closing the reader
> > end of the pipe.
> >
> > Ignoring the SIGPIPE will cause the write operation to return an
> > error which will be logged as "io_send: Broken pipe".
>
> Ive been suggesting using MSG_NOSIGNAL, do you have anything against it?
>
> MSG_NOSIGNAL (since Linux 2.2)Requests not to send SIGPIPE on errors
> on stream oriented sockets when the other end breaks the connection.
> The EPIPE error is still returned.
> (https://linux.die.net/man/2/send)
>
> > ---
> >  src/main.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/src/main.c b/src/main.c
> > index 4716f5388..c62886593 100644
> > --- a/src/main.c
> > +++ b/src/main.c
> > @@ -691,7 +691,7 @@ int main(int argc, char *argv[])
> >         uint16_t sdp_mtu = 0;
> >         uint32_t sdp_flags = 0;
> >         int gdbus_flags = 0;
> > -       guint signal, watchdog;
> > +       guint signal_source, watchdog;
> >         const char *watchdog_usec;
> >
> >         init_defaults();
> > @@ -721,7 +721,11 @@ int main(int argc, char *argv[])
> >
> >         event_loop = g_main_loop_new(NULL, FALSE);
> >
> > -       signal = setup_signalfd();
> > +       signal_source = setup_signalfd();
> > +
> > +       /* Ignore SIGPIPE, a broken pipe error will be returned from write
> > +        * attempts to a pipe with no readers */
> > +       signal(SIGPIPE, SIG_IGN);
> >
> >         __btd_log_init(option_debug, option_detach);
> >
> > @@ -809,7 +813,7 @@ int main(int argc, char *argv[])
> >
> >         sd_notify(0, "STATUS=Quitting");
> >
> > -       g_source_remove(signal);
> > +       g_source_remove(signal_source);
> >
> >         plugin_cleanup();
> >
> > --
> > 2.19.1
> >
>
>
> --
> Luiz Augusto von Dentz