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SubjectRe: [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH
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


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