Messages in this thread | | | From | Denys Vlasenko <> | Date | Mon, 14 Feb 2011 18:57:31 +0100 | Subject | Re: [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH |
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On Mon, Feb 14, 2011 at 6:39 PM, Oleg Nesterov <oleg@redhat.com> wrote: > On 02/14, Denys Vlasenko wrote: >> >> On Mon, Feb 14, 2011 at 4:31 PM, Oleg Nesterov <oleg@redhat.com> wrote: >> > On 02/13, Denys Vlasenko wrote: >> >> >> >> $ strace -tt sleep 30 >> >> 23:02:15.619262 execve("/bin/sleep", ["sleep", "30"], [/* 30 vars */]) = 0 >> >> ... >> >> 23:02:15.622112 nanosleep({30, 0}, NULL) = ? ERESTART_RESTARTBLOCK (To be restarted) >> >> 23:02:23.781165 --- SIGSTOP (Stopped (signal)) @ 0 (0) --- >> >> 23:02:23.781251 --- SIGSTOP (Stopped (signal)) @ 0 (0) --- >> >> (I forgot again why we see it twice. Another quirk I guess...) >> > >> > (this is correct, the tracee reports the signal=SIGSTOP, then >> > it reports it actually stopps with exit_code=SIGSTOP) >> >> Ah, I see. Is there any way debugger can distinguish between these two >> different stops? > > IIRC, the (only?) way to distinguish is to check last_siginfo != NULL > via ptrace(PTRACE_GETSIGINFO).
What do you think strace needs to do when it sees second SIGSTOP (meaning "in theory", not "on current kernel which may be buggy")?
ptrace(PTRACE_SYSCALL, $PID, 0x1, 0)? nothing? something else?
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