Messages in this thread | | | Date | Mon, 18 Aug 2003 20:39:29 -0700 (PDT) | Subject | Re: Debug: sleeping function called from invalid context | From | "Randy.Dunlap" <> |
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> "Randy.Dunlap" <rddunlap@osdl.org> wrote: >> >> Debug: sleeping function called with interrupts disabled at >> include/asm/uaccess.h:473 > > OK, now my vague understanding of what's going on is that the app has chosen > to disable local interupts (via iopl()) and has taken a vm86 trap. I guess > we'd see the same thing if the app performed some sleeping syscall while > interrupts are disabled. > > If that is correct then it really is just a false positive. > > It could also point at a bug in the application; it is presumably disabling > interrupts for some form of locking, atomicity or timing guarantee. But it > will not lock against other CPUs and the fact that it trapped into the > kernel indicates tat it may not be getting the atomicity which it desires.
Call Trace: [<c0120d93>] __might_sleep+0x53/0x74 [<c010d001>] save_v86_state+0x71/0x1f0 [<c010dbd5>] handle_vm86_fault+0xc5/0xa90 [<c019cac8>] ext3_file_write+0x28/0xc0 [<c011cd96>] __change_page_attr+0x26/0x220 [<c010b310>] do_general_protection+0x0/0x90 [<c010a69d>] error_code+0x2d/0x40 [<c0109657>] syscall_call+0x7/0xb
My (more) vague understanding is that X(?) got the kernel to do_general_protection() somehow, but change_page_attr() does this: spin_lock_irqsave(&cpa_lock, flags); in arch/i386/mm/pageattr.c (I'm on a UP box), so irqs are disabled by the kernel and then we calls put_user() with a spinlock held.
~Randy [betting I understand it less than Andrew]
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