Re: [PATCH 1/1] ptrace: make sure do_wait() won't hang afterPTRACE_ATTACH

[Jan Kratochvil]

On Mon, 14 Feb 2011 00:01:47 +0100, Denys Vlasenko wrote:
> * sleep runs in nanosleep
> * SIGSTOP arrives, strace sees it
> * strace logs it and allows it via ptrace(PTRACE_SYSCALL, ..., SIGSTOP)
> * sleep process enters group-stop

The last point breaks the documented behavior of ptrace:
	If data is nonzero and not SIGSTOP, it is interpreted as a signal to
	be delivered to the child; otherwise, no signal is delivered.

I do not see it would affect gdb.  strace will change its behavior when
SIGSTOP is sent to its tracee although the new behavior may be OK.

It is more a subject of apps compatibility testing with such a kernel change.


> * nothing happens until some other signal arrives
> * say, SIGCONT arrives

What if other signal arrives?  The tracer probably should not be notified as
the tracee is in a group-stop.


> * strace logs it and allows it via ptrace(PTRACE_SYSCALL, ..., SIGCONT)


Thanks,
Jan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/