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Commit 20f34165 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

Merge tag 'ras_for_4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras into acpi-apei 

Pull GHES changes for 4.2 from Borislav Petkov:

"GHES: Seriously speedup and cleanup NMI handler (Jiri Kosina and Borislav Petkov)

This is the result of us seeing this during boot

[   24.332560] INFO: NMI handler (ghes_notify_nmi) took too long to run: 3.265 msecs
[   24.332567] INFO: NMI handler (ghes_notify_nmi) took too long to run: 5.946 msecs
[   24.332568] INFO: NMI handler (ghes_notify_nmi) took too long to run: 5.948 msecs

and a report of people running perf stat and the machine softlocking.
"hest_disable" was helping in this case, which made us look at that
particular NMI handler. It was grabbing a lock each time it is run and
on each CPU. But this is not needed as the GHES sources are global and
they need only a single reader.

This patchset does that and cleans up the handler in the process."

* tag 'ras_for_4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras:
  GHES: Make NMI handler have a single reader
  GHES: Elliminate double-loop in the NMI handler
  GHES: Panic right after detection
  GHES: Carve out the panic functionality
  GHES: Carve out error queueing in a separate function
parents 5ebe6afa 6fe9e7c2

drivers/acpi/apei/ghes.c

+55 −53
Original line number Diff line number Diff line
@@ -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);
@@ -797,73 +797,75 @@ static void ghes_print_queued_estatus(void) 
	}

}



static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)

/* Save estatus for further processing in IRQ context */

static void __process_error(struct ghes *ghes)

{

	struct ghes *ghes, *ghes_global = NULL;

	int sev, sev_global = -1;

	int ret = NMI_DONE;

#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG

	u32 len, node_len;

	struct ghes_estatus_node *estatus_node;

	struct acpi_hest_generic_status *estatus;



	raw_spin_lock(&ghes_nmi_lock);

	list_for_each_entry_rcu(ghes, &ghes_nmi, list) {

		if (ghes_read_estatus(ghes, 1)) {

			ghes_clear_estatus(ghes);

			continue;

		}

		sev = ghes_severity(ghes->estatus->error_severity);

		if (sev > sev_global) {

			sev_global = sev;

			ghes_global = ghes;

		}

		ret = NMI_HANDLED;

	}

	if (ghes_estatus_cached(ghes->estatus))

		return;



	if (ret == NMI_DONE)

		goto out;

	len = cper_estatus_len(ghes->estatus);

	node_len = GHES_ESTATUS_NODE_LEN(len);



	if (sev_global >= GHES_SEV_PANIC) {

	estatus_node = (void *)gen_pool_alloc(ghes_estatus_pool, node_len);

	if (!estatus_node)

		return;



	estatus_node->ghes = ghes;

	estatus_node->generic = ghes->generic;

	estatus = GHES_ESTATUS_FROM_NODE(estatus_node);

	memcpy(estatus, ghes->estatus, len);

	llist_add(&estatus_node->llnode, &ghes_estatus_llist);

#endif

}



static void __ghes_panic(struct ghes *ghes)

{

	oops_begin();

	ghes_print_queued_estatus();

		__ghes_print_estatus(KERN_EMERG, ghes_global->generic,

				     ghes_global->estatus);

	__ghes_print_estatus(KERN_EMERG, ghes->generic, ghes->estatus);



	/* reboot to log the error! */

	if (panic_timeout == 0)

		panic_timeout = ghes_panic_timeout;

	panic("Fatal hardware error!");

}



static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)

{

	struct ghes *ghes;

	int sev, ret = NMI_DONE;



	if (!atomic_add_unless(&ghes_in_nmi, 1, 1))

		return ret;



	list_for_each_entry_rcu(ghes, &ghes_nmi, list) {

#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG

		u32 len, node_len;

		struct ghes_estatus_node *estatus_node;

		struct acpi_hest_generic_status *estatus;

#endif

		if (!(ghes->flags & GHES_TO_CLEAR))

		if (ghes_read_estatus(ghes, 1)) {

			ghes_clear_estatus(ghes);

			continue;

#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG

		if (ghes_estatus_cached(ghes->estatus))

			goto next;

		/* Save estatus for further processing in IRQ context */

		len = cper_estatus_len(ghes->estatus);

		node_len = GHES_ESTATUS_NODE_LEN(len);

		estatus_node = (void *)gen_pool_alloc(ghes_estatus_pool,

						      node_len);

		if (estatus_node) {

			estatus_node->ghes = ghes;

			estatus_node->generic = ghes->generic;

			estatus = GHES_ESTATUS_FROM_NODE(estatus_node);

			memcpy(estatus, ghes->estatus, len);

			llist_add(&estatus_node->llnode, &ghes_estatus_llist);

		}

next:

#endif



		sev = ghes_severity(ghes->estatus->error_severity);

		if (sev >= GHES_SEV_PANIC)

			__ghes_panic(ghes);



		if (!(ghes->flags & GHES_TO_CLEAR))

			continue;



		__process_error(ghes);

		ghes_clear_estatus(ghes);



		ret = NMI_HANDLED;

	}



#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG

	irq_work_queue(&ghes_proc_irq_work);

#endif



out:

	raw_spin_unlock(&ghes_nmi_lock);

	atomic_dec(&ghes_in_nmi);

	return ret;

}