Re: [PATCH] rwsem generic spinlock: use IRQ save/restore spinlocks

[Kevin Hilman <khilman@deeprootsystems.com>]

Kevin Hilman <khilman@deeprootsystems.com> writes:

> rwsems can be used with IRQs disabled, particularily in early boot
> before IRQs are enabled.  Currently the spin_unlock_irq() usage in the
> slow-path will unconditionally enable interrupts and cause problems
> early in boot where interrupts are not yet initialized or enabled.
>
> This patch uses save/restore versions of IRQ spinlocks in the slowpath
> to ensure interrupts are not unintentionally enabled in the case where
> the rwsem is used with IRQs disabled.
>
> Idea for this fix suggested by H. Peter Anvin.
>
> Tested on TI OMAP3-based platform (ARM Cortex-A8)
>
> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
> Cc: Rabin Vincent <rabin@rab.in>
> Cc: H. Peter Anvin <hpa@zytor.com>
> LKML-Reference: <alpine.LFD.2.00.1004010904540.3707@i5.linux-foundation.org>
> Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>

For the benefit of the l-o archives...

This patch was merged into mainline in .34-rc6 and fixes potential
deadlocks on boot, seen especially when using the SLUB allocator.

Kevin