Re: [PATCH v8] blk-mq: Rework blk-mq timeout handling again

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On Fri, 2018-05-11 at 15:21 -0600, Jens Axboe wrote:
> On 5/11/18 3:08 PM, Bart Van Assche wrote:
> blk_mq_rq_update_aborted_gstate(rq, gstate);
> > +	union blk_deadline_and_state das = READ_ONCE(rq->das);
> > +	unsigned long now = jiffies;
> > +	int32_t diff_jiffies = das.deadline - now;
> > +	int32_t diff_next = das.deadline - data->next;
> > +	enum mq_rq_state rq_state = das.state;
> 
> Why the int32_t types? Just use an int/unsigned int?

The code that uses the diff_jiffies and diff_next variables can only work
correctly if the subtraction results are truncated to 32 bits. Hence the
use of the int32_t data types to make this explicit. I think using int32_t
instead of int makes this code easier to read.

> > @@ -103,37 +97,119 @@ extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);
> >  
> >  void blk_mq_release(struct request_queue *q);
> >  
> > +#if defined(CONFIG_ARC) ||						\
> > +    defined(CONFIG_ARM) && defined(CONFIG_CPU_THUMBONLY) ||		\
> > +    defined(CONFIG_C6x) || defined(CONFIG_H8300) ||			\
> > +    defined(CONFIG_HEXAGON) || defined(CONFIG_MICROBLAZE) ||		\
> > +    defined(CONFIG_MIPS) && !defined(CONFIG_64BIT) ||			\
> > +    defined(CONFIG_NDS32) || defined(CONFIG_NIOS) ||			\
> > +    defined(CONFIG_OPENRISC) || defined(CONFIG_PPC32) ||		\
> > +    defined(CONFIG_SUPERH) || defined(CONFIG_UML) || defined(CONFIG_UNICORE32)
> > +#undef CONFIG_ARCH_HAS_CMPXCHG64
> > +#else
> > +#define CONFIG_ARCH_HAS_CMPXCHG64
> > +#endif
> 
> I think the encapsulation of blk_mq_set_rq_state() in terms of lock vs
> cmpxchg64 is fine, but this does not belong in the block layer.
> 
> > +	/* Only used if CONFIG_ARCH_HAS_CMPXCHG64 is not defined. */
> > +	spinlock_t das_lock;
> 
> Let's put it under an if defined() then.

OK, I will move CONFIG_ARCH_HAS_CMPXCHG64 into arch/*/Kconfig and I will
surround spinlock_t das_lock with #if defined(...) / #endif.

Thanks,

Bart.






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