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GHES: Make NMI handler have a single reader

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Since GHES sources are global, we theoretically need only a single CPU
reading them per NMI instead of a thundering herd of CPUs waiting on a
spinlock in NMI context for no reason at all.

Do that.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Borislav Petkov <bp@suse.de>
This commit is contained in:
Jiri Kosina 2015-03-27 10:05:00 +01:00 committed by Borislav Petkov
parent 2383844d48
commit 6fe9e7c26a
1 changed files with 7 additions and 5 deletions
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12
drivers/acpi/apei/ghes.c
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@ -729,10 +729,10 @@ static struct llist_head ghes_estatus_llist;
static struct irq_work ghes_proc_irq_work;
/*
* NMI may be triggered on any CPU, so ghes_nmi_lock is used for
* mutual exclusion.
* NMI may be triggered on any CPU, so ghes_in_nmi is used for
* having only one concurrent reader.
*/
static DEFINE_RAW_SPINLOCK(ghes_nmi_lock);
static atomic_t ghes_in_nmi = ATOMIC_INIT(0);
static LIST_HEAD(ghes_nmi);
@ -840,7 +840,9 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
struct ghes *ghes;
int sev, ret = NMI_DONE;
raw_spin_lock(&ghes_nmi_lock);
if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
return ret;
list_for_each_entry_rcu(ghes, &ghes_nmi, list) {
if (ghes_read_estatus(ghes, 1)) {
ghes_clear_estatus(ghes);
@ -863,7 +865,7 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
irq_work_queue(&ghes_proc_irq_work);
#endif
raw_spin_unlock(&ghes_nmi_lock);
atomic_dec(&ghes_in_nmi);
return ret;
}