Messages in this thread | | | Date | Fri, 11 Jul 2014 18:09:36 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH] ARM: Fix preemption disable in iwmmxt_task_enable() |
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On Fri, Jul 11, 2014 at 10:10:13AM +0100, Sebastian Hesselbarth wrote: > commit 431a84b1a4f7d1a0085d5b91330c5053cc8e8b12 > ("ARM: 8034/1: Disable preemption in iwmmxt_task_enable()") > introduced macros {inc,dec}_preempt_count to iwmmxt_task_enable > to make it run with preemption disabled. > > Unfortunately, other functions in iwmmxt.S also use concan_{save,dump,load} > sections located in iwmmxt_task_enable() to deal with iWMMXt coprocessor. > This causes an unbalanced preempt_count due to excessive dec_preempt_count > and destroyed return addresses in callers of concan_ labels due to a register > collision:
Indeed, I missed this part completely.
> --- a/arch/arm/kernel/iwmmxt.S > +++ b/arch/arm/kernel/iwmmxt.S > @@ -94,13 +94,19 @@ ENTRY(iwmmxt_task_enable) > > mrc p15, 0, r2, c2, c0, 0 > mov r2, r2 @ cpwait > + bl concan_save > > - teq r1, #0 @ test for last ownership > - mov lr, r9 @ normal exit from exception > - beq concan_load @ no owner, skip save > +#ifdef CONFIG_PREEMPT_COUNT > + get_thread_info r10 > +#endif > +4: dec_preempt_count r10, r3 > + mov pc, r9 @ normal exit from exception > > concan_save: > > + teq r1, #0 @ test for last ownership > + beq concan_load @ no owner, skip save > + > tmrc r2, wCon > > @ CUP? wCx > @@ -175,10 +181,6 @@ concan_load: > tmcr wCon, r2 > > 3: > -#ifdef CONFIG_PREEMPT_COUNT > - get_thread_info r10 > -#endif > -4: dec_preempt_count r10, r3 > mov pc, lr
It looks fine to me. One optimisation you could do is to replace a couple of beq 3f with moveq pc, lr.
-- Catalin
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