diff options
| author | Jiri Kosina <jkosina@suse.cz> | 2015-03-27 10:05:00 +0100 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2015-04-27 21:35:33 +0200 |
| commit | 6fe9e7c26a97105645fd24f264f1b94e21aade3e (patch) | |
| tree | a636b710834338a34af1dbc932afa1ced659e03a /drivers/acpi/apei/ghes.c | |
| parent | 2383844d4850888cfdf6d202563d2ddb4125a4e9 (diff) | |
| download | lwn-6fe9e7c26a97105645fd24f264f1b94e21aade3e.tar.gz lwn-6fe9e7c26a97105645fd24f264f1b94e21aade3e.zip | |
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/ghes.c')
| -rw-r--r-- | drivers/acpi/apei/ghes.c | 12 |
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; } |