Messages in this thread | ![/](/images/icornerl.gif) | | From | "Manfred Spraul" <> | Subject | Re: [PATCH] Longstanding elf fix (2.4.3 fix) | Date | Mon, 23 Apr 2001 23:54:22 +0200 |
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> Well looking a little more closely than I did last night it looks like > access_process_vm (called from ptrace) can cause what amounts to a > page fault at pretty arbitrary times.
It's also used for several /proc/<pid> files.
I remember that I got crashes with concurrent exec+cat /proc/<pid>/cmdline until down(mmap_sem) was added into setup_arg_pages().
> I'm actually a little curious what the big kernel lock in ptrace buys > us. I suspect it could be a performance issue with user mode linux. > Where you have multiple processes being ptraced at the same time.
I checked it a few months ago, and the lock is only required to prevent multiple concurrent attaches to the same process and concorrent ptrace/suid exec (in fs/exec.c, compute_creds)
-- Manfred
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