Messages in this thread | | | Date | Tue, 30 May 2023 09:59:24 +0800 | Subject | Re: [PATCH v5 1/3] genirq: Use hlist for managing resend handlers | From | "Liao, Chang" <> |
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Hi, Thomas
在 2023/5/30 5:51, Thomas Gleixner 写道: > On Mon, May 29 2023 at 15:57, Chang Liao wrote: >> 在 2023/5/19 21:49, Shanker Donthineni 写道: >>> diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h >>> index 844a8e30e6de..d9451d456a73 100644 >>> --- a/include/linux/irqdesc.h >>> +++ b/include/linux/irqdesc.h >>> @@ -102,6 +102,9 @@ struct irq_desc { >>> int parent_irq; >>> struct module *owner; >>> const char *name; >>> +#ifdef CONFIG_HARDIRQS_SW_RESEND >>> + struct hlist_node resend_node; >>> +#endif >>> } ____cacheline_internodealigned_in_smp; >> >> Although there is no documented rule that limits the change of the KABI >> struct irq_desc, it is still better to keep the irq_desc definition >> stable. > > Please read and understand: > > Documentation/process/stable-api-nonsense.rst > > If you want KABI, then that's _YOUR_ problem, period.
Thanks for the guide.
> >>> -/* Bitmap to handle software resend of interrupts: */ >>> -static DECLARE_BITMAP(irqs_resend, IRQ_BITMAP_BITS); >>> +/* hlist_head to handle software resend of interrupts: */ >>> +static HLIST_HEAD(irq_resend_list); >>> +static DEFINE_RAW_SPINLOCK(irq_resend_lock); >> >> What is the benefit of using hlist here? If you want to enjoy the >> low latency of querying elements by key, you must define a hlist table >> with a reasonable number of buckets. Otherwise, I don't think the time >> complexity of hlist is better than a regular double-linked list, >> right? > > What's complex about hlist in this case? Please explain.
Honestly, it is not about the complexity. Perhaps I do not understand the usage of hlist very deeply. I have searched some codes in the kernel and found that hlist is always used to speed up arbitrary querying, such as searching a registered kprobe by address. Back to this patch, these resend IRQs are organized in a sequence list actually, and traveled one by one to handle. Further, by comparing the difference between hlist_empty, hlist_add_head, hlist_del_init, and their counterparts in list, it looks like a regular linked list is also good enough.
Thanks.
> > Thanks, > > tglx
-- BR Liao, Chang
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