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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Mon, 19 Nov 2018 11:22:15 +0200
Message-ID: <CABBYNZ+Nkbb2vUXVD6FY4+_ZJEqjgfXh=ONn7JYD9nyrx4E50Q@mail.gmail.com>
Subject: Re: [PATCH BlueZ] core: Catch SIGPIPE
To:     gbenhaim@augury.com
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
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Sender: linux-bluetooth-owner@vger.kernel.org
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Hi Gal,

On Sat, Nov 17, 2018 at 10:48 PM Gal Ben Haim <gbenhaim@augury.com> wrote:
>
> i don't think it works at all... bluetoothd is still exiting with SIGPIPE.
> i'm a bit lost with fixing this, I tried few methods that were
> suggested here and the only one that actually worked is to ignore the
> signal.
>
> please advise how do you want to proceed with this..

We might be better of switching to socketpair instead of pipe2 then,
not only we can fix this problem using MSG_NOSIGNAL but also use
sendmsg and setting auxiliary data which can be used to set things
like the offset.

> On Sat, Nov 17, 2018 at 10:41 PM Gal Ben Haim <gbenhaim@augury.com> wrote:
> >
> > actually it does not log the broken pipe message, is it because errno
> > isn't set before the signal handler is done?
> > what do you think?
> > On Sat, Nov 17, 2018 at 8:00 AM 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.
> > >
> > > Catching SIGPIPE will cause the write call to return an EPIPE error
> > > which will be logged as "io_send: Broken pipe".
> > > ---
> > >  src/main.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/src/main.c b/src/main.c
> > > index 4716f5388..54cdb8d3f 100644
> > > --- a/src/main.c
> > > +++ b/src/main.c
> > > @@ -533,6 +533,8 @@ static gboolean signal_handler(GIOChannel *channel, GIOCondition cond,
> > >         case SIGUSR2:
> > >                 __btd_toggle_debug();
> > >                 break;
> > > +       case SIGPIPE:
> > > +               break;
> > >         }
> > >
> > >         return TRUE;
> > > @@ -549,6 +551,7 @@ static guint setup_signalfd(void)
> > >         sigaddset(&mask, SIGINT);
> > >         sigaddset(&mask, SIGTERM);
> > >         sigaddset(&mask, SIGUSR2);
> > > +       sigaddset(&mask, SIGPIPE);
> > >
> > >         if (sigprocmask(SIG_BLOCK, &mask, NULL) < 0) {
> > >                 perror("Failed to set signal mask");
> > > --
> > > 2.19.1
> > >


-- 
Luiz Augusto von Dentz