Ingo Molnar 86998aa653 [PATCH] genirq core: fix handle_level_irq() ... while porting the -rt tree to 2.6.18-rc7 i noticed the following screaming-IRQ scenario on an SMP system: 2274 0Dn.:1 0.001ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.010ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.020ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.029ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.039ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.048ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.058ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.068ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.077ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.087ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) 2274 0Dn.:1 0.097ms: do_IRQ+0xc/0x103 <= (ret_from_intr+0x0/0xf) as it turns out, the bug is caused by handle_level_irq(), which if it races with another CPU already handling this IRQ, it _unmasks_ the IRQ line on the way out. This is not how 2.6.17 works, and we introduced this bug in one of the early genirq cleanups right before it went into -mm. (the bug was not in the genirq patchset for a long time, and we didnt notice the bug due to the lack of -rt rebase to the new genirq code. -rt, and hardirq-preemption in particular opens up such races much wider than anything else.) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>		2006-09-19 07:57:20 -07:00
..
Makefile	[PATCH] genirq: add irq-chip support	2006-06-29 10:26:24 -07:00
autoprobe.c	[PATCH] genirq: add handle_bad_irq()	2006-06-29 10:26:24 -07:00
chip.c	[PATCH] genirq core: fix handle_level_irq()	2006-09-19 07:57:20 -07:00
handle.c	[PATCH] kerneldoc for handle_bad_irq()	2006-09-01 11:39:09 -07:00
internals.h	[PATCH] genirq: more verbose debugging on unexpected IRQ vectors	2006-06-29 10:26:25 -07:00
manage.c	[PATCH] genirq: {en,dis}able_irq_wake() need refcounting too	2006-07-31 13:28:36 -07:00
migration.c	[PATCH] genirq: cleanup: merge pending_irq_cpumask[] into irq_desc[]	2006-06-29 10:26:22 -07:00
proc.c	[PATCH] genirq: cleanup: no_irq_type -> no_irq_chip rename	2006-06-29 10:26:25 -07:00
resend.c	[PATCH] genirq: fix typo in IRQ resend	2006-09-16 12:54:30 -07:00
spurious.c	[PATCH] irq-flags: generic irq: Use the new IRQF_ constants	2006-07-02 13:58:49 -07:00