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authorJiri Kosina <jkosina@suse.cz>2015-03-27 10:05:00 +0100
committerBorislav Petkov <bp@suse.de>2015-04-27 21:35:33 +0200
commit6fe9e7c26a97105645fd24f264f1b94e21aade3e (patch)
treea636b710834338a34af1dbc932afa1ced659e03a /drivers/acpi/apei
parent2383844d4850888cfdf6d202563d2ddb4125a4e9 (diff)
downloadlinux-6fe9e7c26a97105645fd24f264f1b94e21aade3e.tar.bz2
GHES: Make NMI handler have a single reader
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>
Diffstat (limited to 'drivers/acpi/apei')
-rw-r--r--drivers/acpi/apei/ghes.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 94a44bad5576..2bfd53cbfe80 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -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;
}