Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Sun, May 19, 2013 at 12:06:19PM -0400, Steven Rostedt wrote:
> On Sun, 2013-05-19 at 16:34 +0300, Michael S. Tsirkin wrote:
> 
> > Right but we need to keep it working on upstream as well.
> > If I do preempt_enable under a spinlock upstream won't it
> > try to sleep under spinlock?
> 
> No it wont. A spinlock calls preempt_disable implicitly, and a
> preempt_enable() will not schedule unless preempt_count is zero, which
> it wont be under a spinlock.
> 
> If it did, there would be lots of bugs all over the place because this
> is done throughout the kernel (a preempt_enable() under a spinlock).
> 
> In other words, don't ever use preempt_enable_no_resched().
> 
> -- Steve
> 


OK I get it. So let me correct myself. The simple code
that does something like this under a spinlock:
>       preempt_disable
>       pagefault_disable
>       error = copy_to_user
>       pagefault_enable
>       preempt_enable
>
is not doing anything wrong and should not get a warning,
as long as error is handled correctly later.
Right?

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>




[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]