Messages in this thread | | | Date | Wed, 2 Sep 2009 19:28:09 -0400 | From | Tom Horsley <> | Subject | ptrace & /proc deadlock due to mm_for_maps cred_guard_mutex patch |
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The redhat bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=520206#c2
describes a test program that demonstrates an apparent deadlock ptrace can get into as a result of the patch:
commit 704b836cbf19e885f8366bccb2e4b0474346c02d Author: Oleg Nesterov <oleg@redhat.com> Date: Fri Jul 10 03:27:40 2009 +0200 mm_for_maps: take ->cred_guard_mutex to fix the race with exec
ptrace hangs attempting to read the newly exec'ed debugged child process /proc/pid/maps file, and the child is obviously never going to advance as long as it is stopped by ptrace.
I haven't seen any activity on the bugzilla, so since this was a kernel.org patch I figured I'd mention it over here.
As the bugzilla says, it is possible to work around this by single stepping the debugged process before reading the maps file.
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