On 07/10/2013 10:00:33 PM, tiejun.chen wrote:
On 07/11/2013 03:15 AM, Scott Wood wrote:
On 07/10/2013 01:02:19 AM, Tiejun Chen wrote:
We should ensure the preemption cannot occur while calling
get_paca()
insdide hard_irq_disable(), otherwise the paca_struct may be the
wrong one just after. And btw, we may update timing stats in this
case.
The soft-ee mechanism depends on accessing the PACA directly via r13
to avoid
this. We probably should be using inline asm to read was_enabled
rather than
Yes.
hoping the compiler doesn't do anything silly.
Do you recommend I should directly replace get_paca() with local_paca
inside hard_irq_disable()?
#define hard_irq_disable() do { \
u8 _was_enabled = get_paca()->soft_enabled; \
-> u8 _was_enabled = local_paca->soft_enabled;
But is this safe for all scenarios?
get_paca() is just a #define for local_paca. It won't make a
difference, other than to evade the debug check.
In practice, it's unlikely that GCC would do anything other than a load
directly from r13, but to be sure we should use inline asm to do the
load, just like arch_local_save_flags and arch_local_irq_disable do.
-Scott
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