Messages in this thread | | | Date | Wed, 22 Sep 2004 15:14:01 -0500 | Subject | Hotplug: crash in sys_clone()/do_fork() | From | Linas Vepstas <> |
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Hi,
I'm tripping over a race condition involving file handling. I can consistently crash here:
TASK: c0000000fd6dc040[10448] 'ifdown' THREAD: c0000000f3310000 Call Trace: Sep 22 14:29:21 marulp1 kernel: [c0000000f3313b10] [c0000000000506c4] .copy_files+0x400/0x414 (unreliable) [c0000000f3313bd0] [c00000000005161c] .copy_process+0x660/0x12bc [c0000000f3313ce0] [c000000000052318] .do_fork+0xa0/0x25c [c0000000f3313dc0] [c0000000000159c8] .sys_clone+0x5c/0x74 [c0000000f3313e30] [c000000000010a88] .ppc_clone+0x8/0xc
The problem seems to be that one of the file pointers is breifly set to (int32)-1 even on a 64-bit machine. The part of copy_process() that gets mashed by this is:
for (i = open_files; i != 0; i--) { struct file *f = *old_fds++; if (f) get_file(f); <== derefs f, which is -1 *new_fds++ = f; }
By inserting if(f==(void*)0xffffffffUL) printk ... I can find out that i=230 is the one with the problem and open_files=256! I haven't yet found who set struct file * to a -1.
I'm generting this behaviour with a hotplug event that is causing ifdown and ifup to run simultaneously. (The device driver was shut down and restarted, causing simultaneous hotplug events). Although the above stack shows ifdown getting clobbered, I've also seen pci.agent be the process that suffers.
The problem goes away if I insert a sleep of about half-a-second or more between the device driver shutdown and startup.
Affected machine is a ppc64 power4 box. I've seen the problem for a long time (months?), including monday's bk clone of bkbits of 2.6.9-rc2; waiting for this bug "to fix itself" doesn't seem to be working.
--linas
p.s. am I supposed to be using the OSDL bugzilla to report & track bugs like this? - 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/
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