[PATCH 1/3] xenoprof fixes: sleep with interrupts disabled

[Markus Armbruster <armbru@redhat.com>]

Ill-advised use of on_each_cpu() can lead to sleep with interrupts
disabled.  This is best explained with a backtrace:

BUG: sleeping function called from invalid context at /home/armbru/linux-2.6.tip-xen-quintela.hg/mm/slab.c:2783
in_atomic():0, irqs_disabled():1
 [<c0104f36>] show_trace+0x13/0x15
 [<c0105439>] dump_stack+0x18/0x1c
 [<c01161ac>] __might_sleep+0x9f/0xa7
 [<c0158823>] __kmalloc+0x65/0x110
 [<c018e01d>] proc_create+0x8d/0xe2
 [<c018e12d>] proc_mkdir_mode+0x1a/0x4d
 [<c018e173>] proc_mkdir+0x13/0x15
 [<c013de9b>] register_handler_proc+0x90/0x9e
 [<c013d729>] setup_irq+0xdf/0xf5
 [<c013d7a9>] request_irq+0x6a/0x8a
 [<c0231817>] bind_virq_to_irqhandler+0xe3/0x101
 [<f4c83b02>] bind_virq_cpu+0x28/0x62 [oprofile]
 [<c0121453>] on_each_cpu+0x36/0x5d
 [<f4c83c3b>] xenoprof_setup+0x22/0x14a [oprofile]
 [<f4c820bf>] oprofile_setup+0x45/0x8b [oprofile]
 [<f4c82fa3>] event_buffer_open+0x3e/0x62 [oprofile]
 [<c0159eda>] __dentry_open+0xc7/0x1b0
 [<c015a034>] nameidata_to_filp+0x20/0x34
 [<c015a078>] do_filp_open+0x30/0x39
 [<c015afe6>] do_sys_open+0x40/0xb0
 [<c015b07f>] sys_open+0x13/0x15
 [<c01048cf>] syscall_call+0x7/0xb

on_each_cpu() disables interrupts.  proc_create() calls passes
GFP_KERNEL to kmalloc().

The patch converts from on_each_cpu() to for_each_cpu(), and then
simplifies things.


diff -rup linux-2.6.16.13-xen/arch/i386/oprofile/xenoprof.c linux-2.6.16.13-xen.patched-1/arch/i386/oprofile/xenoprof.c
--- linux-2.6.16.13-xen/arch/i386/oprofile/xenoprof.c	2006-05-15 10:32:22.000000000 +0200
+++ linux-2.6.16.13-xen.patched-1/arch/i386/oprofile/xenoprof.c	2006-05-15 10:30:49.000000000 +0200
@@ -141,56 +141,40 @@ xenoprof_ovf_interrupt(int irq, void * d
 }
 
 
-static void unbind_virq_cpu(void * info)
-{
-	int cpu = smp_processor_id();
-	if (ovf_irq[cpu] >= 0) {
-		unbind_from_irqhandler(ovf_irq[cpu], NULL);
-		ovf_irq[cpu] = -1;
-	}
-}
-
-
 static void unbind_virq(void)
 {
-	on_each_cpu(unbind_virq_cpu, NULL, 0, 1);
-}
-
-
-int bind_virq_error;
-
-static void bind_virq_cpu(void * info)
-{
-	int result;
-	int cpu = smp_processor_id();
+	int i;
 
-	result = bind_virq_to_irqhandler(VIRQ_XENOPROF,
-					 cpu,
-					 xenoprof_ovf_interrupt,
-					 SA_INTERRUPT,
-					 "xenoprof",
-					 NULL);
-
-	if (result<0) {
-		bind_virq_error = result;
-		printk("xenoprof.c: binding VIRQ_XENOPROF to IRQ failed on CPU "
-		       "%d\n", cpu);
-	} else {
-		ovf_irq[cpu] = result;
+	for_each_cpu(i) {
+		if (ovf_irq[i] >= 0) {
+			unbind_from_irqhandler(ovf_irq[i], NULL);
+			ovf_irq[i] = -1;
+		}
 	}
 }
 
 
 static int bind_virq(void)
 {
-	bind_virq_error = 0;
-	on_each_cpu(bind_virq_cpu, NULL, 0, 1);
-	if (bind_virq_error) {
-		unbind_virq();
-		return bind_virq_error;
-	} else {
-		return 0;
+	int i, result;
+
+	for_each_cpu(i) {
+		result = bind_virq_to_irqhandler(VIRQ_XENOPROF,
+						 i,
+						 xenoprof_ovf_interrupt,
+						 SA_INTERRUPT,
+						 "xenoprof",
+						 NULL);
+
+		if (result < 0) {
+			unbind_virq();
+			return result;
+		}
+
+		ovf_irq[i] = result;
 	}
+		
+	return 0;
 }