Messages in this thread | | | From | Victor Zandy <> | Date | Thu, 9 Mar 2000 17:55:41 -0600 (CST) | Subject | Is PTRACE_ATTACH lazy? |
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On x86 Linux 2.2.12 a valid ptrace call that closely follows a successful PTRACE_ATTACH can fail, with error ESRCH.
For example, I find that if I make two calls like this
ret = ptrace(PTRACE_ATTACH, pid, 0, 0); ret = ptrace(PTRACE_DETACH, pid, 0, 0);
the second call will fail, with ESRCH.
However, if I put some time between the calls, like this
ret = ptrace(PTRACE_ATTACH, pid, 0, 0); usleep(100); ret = ptrace(PTRACE_DETACH, pid, 0, 0);
then the second call will succeed.
My guess is that the traced process has not had its state set to TASK_STOPPED before the second call to ptrace is executed. (Does the traced process need to be scheduled before it will change to TASK_STOPPED?)
Does anyone know for sure why this happens?
Can anyone suggest a workaround that to allow me make one or more ptrace calls immediately after a PTRACE_ATTACH?
Thanks.
Vic Zandy
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