Perhaps this is old news...but...
I can easily create a race when reading /proc/<pid>/stat
(fs/proc/{base.c,array.c}) where a rapidly reading application, such as
"top", starts reading stats for a thread which goes away during the
read. This is easily reproduced with a program that rapidly forks and
exits while top is running.
On inspection, I don't see how the code can expect the thread_struct to
stay around since it is not holding any lock for the duration of its
use. The code could hold the thread_struct's lock (after verifying it
still exists while holding tasklist_lock I would imagine), but for
performance I would think a better solution would be to copy the struct
since stale data is probably ok in this case.
Dereferencing a non-existent thread_struct is clearly not ok.
Would anyone familiar with this code care to comment?
-- -todd - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon May 07 2001 - 21:00:10 EST