[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20110220174827.GA28509@redhat.com>
Date: Sun, 20 Feb 2011 18:48:27 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Denys Vlasenko <vda.linux@...glemail.com>
Cc: Jan Kratochvil <jan.kratochvil@...hat.com>,
torvalds@...ux-foundation.org, Tejun Heo <tj@...nel.org>,
Roland McGrath <roland@...hat.com>,
linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH 1/1] ptrace: make sure do_wait() won't hang after
PTRACE_ATTACH
On 02/20, Denys Vlasenko wrote:
>
> On Sunday 20 February 2011 10:40, Jan Kratochvil wrote:
> > Sure by default GDB does not do anything special, it will respawn (using
> > PTRACE_CONT(SIGSTOP)) any SIGSTOP it sees due to the default setting of:
> > (gdb) handle SIGSTOP
> > Signal Stop Print Pass to program Description
> > SIGSTOP Yes Yes Yes Stopped (signal)
> >
> > Therefore there happens the double SIGSTOP reporting as discussed before:
> > (gdb) run
> > Starting program: /bin/sleep 1h
> > # external kill -STOP <inferior pid>
> > Program received signal SIGSTOP, Stopped (signal).
> > # State: t (tracing stop)
> > (gdb) continue
> > Continuing.
> > Program received signal SIGSTOP, Stopped (signal).
> > # State: t (tracing stop)
> > (gdb) continue
> > Continuing.
> > # State: S (sleeping)
> >
> > Your proposal is I expect:
> > (gdb) run
> > Starting program: /bin/sleep 1h
> > # external kill -STOP <inferior pid>
> > Program received signal SIGSTOP, Stopped (signal).
> > # State: t (tracing stop)
> > (gdb) continue
> > Continuing.
> > # State: T (stopped)
>
> Not exactly. Even after we fix kernel so that it properly preserves
> group-stop across ptrace-stops, gdb will still see TWO
> waitpid:SIGSTOP events, not one.
Yes, I didn't notice the second report doesn't show SIGSTOP twice.
The only important change is
(gdb) continue
Continuing.
- # State: S (sleeping)
+ # State: T (stopped)
> I think you can use similar trick in gdb, so that second message says
> "Program stopped due to signal SIGSTOP, Stopped (signal)",
> not "Program received signal SIGSTOP, Stopped (signal)".
Agreed.
Oleg.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists