Re: BUG in x86 do_page_fault? [was Re: in_atomic doesn't count local_irq_disable?]
From: Linus Torvalds (torvalds_at_osdl.org)
Date: 12/31/03
- Previous message: Jeff Garzik: "Re: [PATCH] pci_set_dac helper"
- In reply to: Srivatsa Vaddagiri: "BUG in x86 do_page_fault? [was Re: in_atomic doesn't count local_irq_disable?]"
- Next in thread: Srivatsa Vaddagiri: "Re: [lhcs-devel] Re: in_atomic doesn't count local_irq_disable?"
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Date: Wed, 31 Dec 2003 11:08:21 -0800 (PST) To: Srivatsa Vaddagiri <vatsa@in.ibm.com>
On Wed, 31 Dec 2003, Srivatsa Vaddagiri wrote:
>
> in_atomic() doesn't seem to return true
> in code sections where IRQ's have been disabled (using
> local_irq_disable).
>
> As a result, I think do_page_fault() on x86 needs to
> be updated to note this fact:
NO.
Please don't do this, it will result in some _really_ nasty problems with
X and other programs that potentially disable interrupts in user space.
Also, there are broken old drivers that potentially have interrupts
disabled, and we shouldn't just oops them. We should have a warning, but
we already do have that: that's what "might_sleep()" does.
So something like this may be appropriate at some point, but not in this
format. At the very least you absolutely _have_ to check for user mode
(possibly in the same place where we now have that
/* It's safe to allow irq's after cr2 has been saved */
comment).
Lnus
> --- fault.c.org Wed Dec 31 18:34:18 2003
> +++ fault.c Wed Dec 31 18:35:02 2003
> @@ -259,7 +259,7 @@
> * If we're in an interrupt, have no user context or are running in an
> * atomic region then we must not take the fault..
> */
> - if (in_atomic() || !mm)
> + if (in_atomic() || irqs_disabled() || !mm)
> goto bad_area_nosemaphore;
>
> down_read(&mm->mmap_sem);
-
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- Previous message: Jeff Garzik: "Re: [PATCH] pci_set_dac helper"
- In reply to: Srivatsa Vaddagiri: "BUG in x86 do_page_fault? [was Re: in_atomic doesn't count local_irq_disable?]"
- Next in thread: Srivatsa Vaddagiri: "Re: [lhcs-devel] Re: in_atomic doesn't count local_irq_disable?"
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