Messages in this thread | | | Subject | Re: Kernel panics on raw I/O stress test | From | Takanori Kawano <> | Date | Fri, 20 Apr 2001 20:44:35 +0900 (JST) |
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> Could you try again with 2.4.4pre4 plus the below patch? > > ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/patches/v2.4/2.4.4pre2/rawio-3
I suppose that 2.4.4-pre4 + rawio-3 patch still has SMP-unsafe raw i/o code and can cause the same panic I reported.
I think the following scenario is possible if there are 3 or more CPUs.
(1) CPU0 enter rw_raw_dev() (2) CPU0 execute alloc_kiovec(1, &iobuf) // drivers/char/raw.c line 309 (3) CPU0 enter brw_kiovec(rw, 1, &iobuf,..) // drivers/char/raw.c line 362 (4) CPU0 enter __wait_on_buffer() (5) CPU0 execute run_task_queue() and wait while buffer_locked(bh) is true. // fs/buffer.c line 152-158 (6) CPU1 enter end_buffer_io_kiobuf() with iobuf allocated at (2) (7) CPU1 execute unlock_buffer() // fs/buffer.c line 1994 (8) CPU0 exit __wait_on_buffer() (9) CPU0 exit brw_kiovec(rw, 1, &iobuf,..) (10) CPU0 execute free_kiovec(1, &iobuf) // drivers/char/raw.c line 388 (11) The task on CPU2 reused the area freed at (10). (12) CPU1 enter end_kio_request() and touch the corrupted iobuf, then panic.
--- Takanori Kawano Hitachi Ltd, Internet Systems Platform Division t-kawano@ebina.hitachi.co.jp
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