linux-kernel - Re: [PATCH 0/8] tip related: radix tree for spareseirq and logical flat clean up

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Date:	Sat, 13 Feb 2010 03:39:25 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	linux-kernel@...r.kernel.org, Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [PATCH  0/8] tip related: radix tree for spareseirq and logical flat clean up

Yinghai Lu <yinghai@...nel.org> writes:

> please check
>
> Subject: [PATCH] x86: use vector_desc instead of vector_irq
>
> Eric pointed out that radix tree version of irq_to_desc will magnify delay on the path
> of handle_irq.
> use vector_desc to reduce the calling of irq_to_desc.

You have missed Xen's handling of handle_irq.  Let's just kill it like:


>From 0fd5a07f0d346aee37524108d74be7d70c0ab753 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman <ebiederm@...ssion.com>
Date: Sat, 13 Feb 2010 03:22:59 -0800
Subject: [PATCH] xen: Remove unnecessary arch specific xen irq functions.

Right now xen's use of the x86 and ia64 handle_irq is just bizarre and very
fragile as it is very non-obvious the function exists and is is used by
code out in drivers/....  Luckily using handle_irq is completly unnecessary,
and we can just use the generic irq apis instead.

This still leaves drivers/xen/events.c as a problematic user of the generic
irq apis it has "static struct irq_info irq_info[NR_IRQS]" but that can be
fixed some other time.

Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
 arch/ia64/include/asm/xen/events.h |    4 ----
 drivers/xen/events.c               |    8 ++++++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/ia64/include/asm/xen/events.h b/arch/ia64/include/asm/xen/events.h
index b8370c8..baa74c8 100644
--- a/arch/ia64/include/asm/xen/events.h
+++ b/arch/ia64/include/asm/xen/events.h
@@ -36,10 +36,6 @@ static inline int xen_irqs_disabled(struct pt_regs *regs)
 	return !(ia64_psr(regs)->i);
 }
 
-static inline void handle_irq(int irq, struct pt_regs *regs)
-{
-	__do_IRQ(irq);
-}
 #define irq_ctx_init(cpu)	do { } while (0)
 
 #endif /* _ASM_IA64_XEN_EVENTS_H */
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index ce602dd..2f84137 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -649,9 +649,13 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
 				int bit_idx = __ffs(pending_bits);
 				int port = (word_idx * BITS_PER_LONG) + bit_idx;
 				int irq = evtchn_to_irq[port];
+				struct irq_desc *desc;
 
-				if (irq != -1)
-					handle_irq(irq, regs);
+				if (irq != -1) {
+					desc = irq_to_desc(irq);
+					if (desc)
+						generic_handle_irq_desc(irq, desc);
+				}
 			}
 		}
 
-- 
1.6.5.2.143.g8cc62

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