From: Roland McGrath <roland@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: utrace-devel@redhat.com, archer@sourceware.org
Subject: Re: gdbstub initial code, v7
Date: Wed, 13 Oct 2010 07:23:00 -0000 [thread overview]
Message-ID: <20101013072346.1F239401B2@magilla.sf.frob.com> (raw)
In-Reply-To: Oleg Nesterov's message of Friday, 10 September 2010 21:20:01 +0200 <20100910192001.GA30490@redhat.com>
> On 09/10, Roland McGrath wrote:
> >
> > > ugdb sets "please stop" flag and does utrace_control(INTERRUPT). However,
> > > in unlikely case the tracee can stop before ->report_signal() reporting
> >
> > I don't think this is the right thing to do. When the intent is explicitly
> > to interrupt, there is no reason to stop before the interruption is
> > complete, i.e. report_signal.
>
> This means that ugdb_report_quiesce() should never return UTRACE_STOP,
> and that is all.
I'm not sure about this.
> But what about multitracing? Suppose that "(gdb) interrupt" happens
> just before, say, do_report_syscall_entry() and another engine wants
> to stop. If ugdb_report_quiesce() doesn't return UTRACE_STOP, then
> gdb will wait until another debugger resumes the tracee.
Yes, I do think that's a problem. We want gdb to report back promptly.
One possibility is to have report_quiesce notice its argument is
UTRACE_EVENT(SYSCALL_ENTRY) and roll back to before the syscall.
That is, it enables SYSCALL_ENTRY and SYSCALL_EXIT reporting, then
its report_syscall_entry uses UTRACE_SIGNAL_ABORT, report_syscall_exit
does syscall_set_return_value(-ERESTARTNOHAND, 0) and then returns
UTRACE_INTERRUPT. Now, we'll reenter a UTRACE_SIGNAL_REPORT callback
"before" the system call, and we can stop there without being in any
sticky situation.
Thanks,
Roland
next prev parent reply other threads:[~2010-10-13 7:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-30 19:02 Oleg Nesterov
2010-08-30 19:20 ` Jan Kratochvil
2010-08-31 7:21 ` Jan Kratochvil
2010-09-02 20:09 ` Oleg Nesterov
2010-09-03 6:40 ` Jan Kratochvil
2010-09-03 19:59 ` Roland McGrath
2010-09-03 20:03 ` Jan Kratochvil
2010-09-03 20:10 ` Roland McGrath
2010-09-03 23:13 ` Oleg Nesterov
2010-09-10 10:15 ` Roland McGrath
2010-09-10 18:32 ` Oleg Nesterov
2010-09-10 19:06 ` Roland McGrath
2010-09-10 19:23 ` Oleg Nesterov
2010-10-13 7:23 ` Roland McGrath [this message]
2010-10-15 14:32 ` Oleg Nesterov
2010-09-03 14:17 ` Frank Ch. Eigler
2010-09-03 23:00 ` Oleg Nesterov
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