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x86/nmi: Push duration printk() to irq context

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Calling printk() from NMI context is bad (TM), so move it to IRQ
context.

In doing so we slightly change (probably wreck) the debugfs
nmi_longest_ns thingy, in that it doesn't update to reflect the
longest, nor does writing to it reset the count.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Link: http://lkml.kernel.org/n/tip-rdw0au56a5ymis1u8p48c12d@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-02-03 18:02:09 +01:00 committed by Ingo Molnar
parent 6a02ad66b2
commit e90c785352
2 changed files with 27 additions and 13 deletions
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3
arch/x86/include/asm/nmi.h
View File

@ -1,6 +1,7 @@
#ifndef _ASM_X86_NMI_H
#define _ASM_X86_NMI_H
#include <linux/irq_work.h>
#include <linux/pm.h>
#include <asm/irq.h>
#include <asm/io.h>
@ -38,6 +39,8 @@ typedef int (*nmi_handler_t)(unsigned int, struct pt_regs *);
struct nmiaction {
struct list_head list;
nmi_handler_t handler;
u64 max_duration;
struct irq_work irq_work;
unsigned long flags;
const char *name;
};

37
arch/x86/kernel/nmi.c
View File

@ -87,6 +87,7 @@ __setup("unknown_nmi_panic", setup_unknown_nmi_panic);
#define nmi_to_desc(type) (&nmi_desc[type])
static u64 nmi_longest_ns = 1 * NSEC_PER_MSEC;
static int __init nmi_warning_debugfs(void)
{
debugfs_create_u64("nmi_longest_ns", 0644,
@ -95,6 +96,20 @@ static int __init nmi_warning_debugfs(void)
}
fs_initcall(nmi_warning_debugfs);
static void nmi_max_handler(struct irq_work *w)
{
struct nmiaction *a = container_of(w, struct nmiaction, irq_work);
int remainder_ns, decimal_msecs;
u64 whole_msecs = ACCESS_ONCE(a->max_duration);
remainder_ns = do_div(whole_msecs, (1000 * 1000));
decimal_msecs = remainder_ns / 1000;
printk_ratelimited(KERN_INFO
"INFO: NMI handler (%ps) took too long to run: %lld.%03d msecs\n",
a->handler, whole_msecs, decimal_msecs);
}
static int __kprobes nmi_handle(unsigned int type, struct pt_regs *regs, bool b2b)
{
struct nmi_desc *desc = nmi_to_desc(type);
@ -110,26 +125,20 @@ static int __kprobes nmi_handle(unsigned int type, struct pt_regs *regs, bool b2
* to handle those situations.
*/
list_for_each_entry_rcu(a, &desc->head, list) {
u64 before, delta, whole_msecs;
int remainder_ns, decimal_msecs, thishandled;
int thishandled;
u64 delta;
before = sched_clock();
delta = sched_clock();
thishandled = a->handler(type, regs);
handled += thishandled;
delta = sched_clock() - before;
delta = sched_clock() - delta;
trace_nmi_handler(a->handler, (int)delta, thishandled);
if (delta < nmi_longest_ns)
if (delta < nmi_longest_ns || delta < a->max_duration)
continue;
nmi_longest_ns = delta;
whole_msecs = delta;
remainder_ns = do_div(whole_msecs, (1000 * 1000));
decimal_msecs = remainder_ns / 1000;
printk_ratelimited(KERN_INFO
"INFO: NMI handler (%ps) took too long to run: "
"%lld.%03d msecs\n", a->handler, whole_msecs,
decimal_msecs);
a->max_duration = delta;
irq_work_queue(&a->irq_work);
}
rcu_read_unlock();
@ -146,6 +155,8 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action)
if (!action->handler)
return -EINVAL;
init_irq_work(&action->irq_work, nmi_max_handler);
spin_lock_irqsave(&desc->lock, flags);
/*