From: Hidetoshi Seto Date: Fri, 8 Dec 2006 10:35:58 +0000 (-0800) Subject: [PATCH] CPEI gets warning at kernel/irq/migration.c:27/move_masked_irq() X-Git-Tag: v2.6.20-rc1~34^2~401 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6e2ac66470976ad7f57e0948572669b2bdfea2d0;p=linux-2.6 [PATCH] CPEI gets warning at kernel/irq/migration.c:27/move_masked_irq() While running my MCA test (hardware error injection) on 2.6.19, I got some warning like following: > BUG: warning at kernel/irq/migration.c:27/move_masked_irq() > > Call Trace: > [] show_stack+0x40/0xa0 > sp=e00000006b2578d0 bsp=e00000006b2510b0 > [] dump_stack+0x30/0x60 > sp=e00000006b257aa0 bsp=e00000006b251098 > [] move_masked_irq+0xb0/0x240 > sp=e00000006b257aa0 bsp=e00000006b251070 > [] move_native_irq+0xe0/0x180 > sp=e00000006b257aa0 bsp=e00000006b251040 > [] iosapic_end_level_irq+0x30/0xe0 > sp=e00000006b257aa0 bsp=e00000006b251020 > [] __do_IRQ+0x170/0x400 > sp=e00000006b257aa0 bsp=e00000006b250fd8 > [] ia64_handle_irq+0x1b0/0x260 > sp=e00000006b257aa0 bsp=e00000006b250fa8 > [] ia64_leave_kernel+0x0/0x280 > sp=e00000006b257aa0 bsp=e00000006b250fa8 > [] _spin_unlock_irqrestore+0x30/0x60 > sp=e00000006b257c70 bsp=e00000006b250f90 It comes from: [kernel/irq/migration.c] 26 if (CHECK_IRQ_PER_CPU(desc->status)) { 27 WARN_ON(1); 28 return; 29 } By putting some printk in kernel, I found that irqbalance is trying to move CPEI which is handled as PER_CPU irq. That's why. CPEI(Corrected Platform Error Interrupt) is ia64 specific irq, is allowed to pin to particular processor which selected by the platform, and even it is PER_CPU but it has set_affinity handler (=iosapic_set_affinity) as same as other IO-SAPIC-level interrupts. (I don't know why, but I guess that there would be typical situation where the handler for migration is needed, such as hotplug - the processor going to be offline/hot-removed.) To shut up this warning, there are 2 way at least: a) fix CPEI stuff b) prohibit setting affinity to PER_CPU irq I'm not sure what stuff of CPEI need to be fixed, but I think that returning error to attempting move PER_CPU irq is useful for all applications since it will never work. Following small patch takes b) style. It works, the warning disappeared and irqbalance still runs well. Signed-off-by: Hidetoshi Seto Cc: Arjan van de Ven Acked-by: Ingo Molnar Acked-by: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c index 9a35266700..61f5c717a8 100644 --- a/kernel/irq/proc.c +++ b/kernel/irq/proc.c @@ -54,7 +54,8 @@ static int irq_affinity_write_proc(struct file *file, const char __user *buffer, unsigned int irq = (int)(long)data, full_count = count, err; cpumask_t new_value, tmp; - if (!irq_desc[irq].chip->set_affinity || no_irq_affinity) + if (!irq_desc[irq].chip->set_affinity || no_irq_affinity || + CHECK_IRQ_PER_CPU(irq_desc[irq].status)) return -EIO; err = cpumask_parse_user(buffer, count, new_value);