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authorChangbin Du <changbin.du@gmail.com>2020-01-11 20:54:27 +0800
committerBorislav Petkov <bp@suse.de>2020-01-11 15:55:39 +0100
commit248ed51048c40d36728e70914e38bffd7821da57 (patch)
tree9b5eed653ff1b880fa2b7ae8c9b9767ed1db2346 /arch/x86/kernel/nmi.c
parent36209766cede1fe9d39f3d3418d93bbf71ad21c4 (diff)
x86/nmi: Remove irq_work from the long duration NMI handler
First, printk() is NMI-context safe now since the safe printk() has been implemented and it already has an irq_work to make NMI-context safe. Second, this NMI irq_work actually does not work if a NMI handler causes panic by watchdog timeout. It has no chance to run in such case, while the safe printk() will flush its per-cpu buffers before panicking. While at it, repurpose the irq_work callback into a function which concentrates the NMI duration checking and makes the code easier to follow. [ bp: Massage. ] Signed-off-by: Changbin Du <changbin.du@gmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20200111125427.15662-1-changbin.du@gmail.com
Diffstat (limited to 'arch/x86/kernel/nmi.c')
-rw-r--r--arch/x86/kernel/nmi.c20
1 files changed, 9 insertions, 11 deletions
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index e676a9916c49..54c21d6abd5a 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -104,18 +104,22 @@ static int __init nmi_warning_debugfs(void)
}
fs_initcall(nmi_warning_debugfs);
-static void nmi_max_handler(struct irq_work *w)
+static void nmi_check_duration(struct nmiaction *action, u64 duration)
{
- struct nmiaction *a = container_of(w, struct nmiaction, irq_work);
+ u64 whole_msecs = READ_ONCE(action->max_duration);
int remainder_ns, decimal_msecs;
- u64 whole_msecs = READ_ONCE(a->max_duration);
+
+ if (duration < nmi_longest_ns || duration < action->max_duration)
+ return;
+
+ action->max_duration = 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);
+ action->handler, whole_msecs, decimal_msecs);
}
static int nmi_handle(unsigned int type, struct pt_regs *regs)
@@ -142,11 +146,7 @@ static int nmi_handle(unsigned int type, struct pt_regs *regs)
delta = sched_clock() - delta;
trace_nmi_handler(a->handler, (int)delta, thishandled);
- if (delta < nmi_longest_ns || delta < a->max_duration)
- continue;
-
- a->max_duration = delta;
- irq_work_queue(&a->irq_work);
+ nmi_check_duration(a, delta);
}
rcu_read_unlock();
@@ -164,8 +164,6 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action)
if (!action->handler)
return -EINVAL;
- init_irq_work(&action->irq_work, nmi_max_handler);
-
raw_spin_lock_irqsave(&desc->lock, flags);
/*