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Commit 33cc2c96 authored by Dan Williams's avatar Dan Williams
Browse files

acpi, nfit: Fix scrub idle detection 



The notification of scrub completion happens within the scrub workqueue.
That can clearly race someone running scrub_show() and work_busy()
before the workqueue has a chance to flush the recently completed work.
Add a flag to reliably indicate the idle vs busy state. Without this
change applications using poll(2) to wait for scrub-completion may
falsely wakeup and read ARS as being busy even though the thread is
going idle and then hang indefinitely.

Fixes: bc6ba808 ("nfit, address-range-scrub: rework and simplify ARS...")
Cc: <stable@vger.kernel.org>
Reported-by: default avatarVishal Verma <vishal.l.verma@intel.com>
Tested-by: default avatarVishal Verma <vishal.l.verma@intel.com>
Reported-by: default avatarLukasz Dorau <lukasz.dorau@intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 1273c253

drivers/acpi/nfit/core.c

+33 −11
Original line number Diff line number Diff line
@@ -1275,7 +1275,7 @@ static ssize_t scrub_show(struct device *dev, 


		mutex_lock(&acpi_desc->init_mutex);

		rc = sprintf(buf, "%d%s", acpi_desc->scrub_count,

				work_busy(&acpi_desc->dwork.work)

				acpi_desc->scrub_busy

				&& !acpi_desc->cancel ? "+\n" : "\n");

		mutex_unlock(&acpi_desc->init_mutex);

	}
@@ -2941,6 +2941,32 @@ static unsigned int __acpi_nfit_scrub(struct acpi_nfit_desc *acpi_desc, 
	return 0;

}



static void __sched_ars(struct acpi_nfit_desc *acpi_desc, unsigned int tmo)

{

	lockdep_assert_held(&acpi_desc->init_mutex);



	acpi_desc->scrub_busy = 1;

	/* note this should only be set from within the workqueue */

	if (tmo)

		acpi_desc->scrub_tmo = tmo;

	queue_delayed_work(nfit_wq, &acpi_desc->dwork, tmo * HZ);

}



static void sched_ars(struct acpi_nfit_desc *acpi_desc)

{

	__sched_ars(acpi_desc, 0);

}



static void notify_ars_done(struct acpi_nfit_desc *acpi_desc)

{

	lockdep_assert_held(&acpi_desc->init_mutex);



	acpi_desc->scrub_busy = 0;

	acpi_desc->scrub_count++;

	if (acpi_desc->scrub_count_state)

		sysfs_notify_dirent(acpi_desc->scrub_count_state);

}



static void acpi_nfit_scrub(struct work_struct *work)

{

	struct acpi_nfit_desc *acpi_desc;
@@ -2951,14 +2977,10 @@ static void acpi_nfit_scrub(struct work_struct *work) 
	mutex_lock(&acpi_desc->init_mutex);

	query_rc = acpi_nfit_query_poison(acpi_desc);

	tmo = __acpi_nfit_scrub(acpi_desc, query_rc);

	if (tmo) {

		queue_delayed_work(nfit_wq, &acpi_desc->dwork, tmo * HZ);

		acpi_desc->scrub_tmo = tmo;

	} else {

		acpi_desc->scrub_count++;

		if (acpi_desc->scrub_count_state)

			sysfs_notify_dirent(acpi_desc->scrub_count_state);

	}

	if (tmo)

		__sched_ars(acpi_desc, tmo);

	else

		notify_ars_done(acpi_desc);

	memset(acpi_desc->ars_status, 0, acpi_desc->max_ars);

	mutex_unlock(&acpi_desc->init_mutex);

}
@@ -3039,7 +3061,7 @@ static int acpi_nfit_register_regions(struct acpi_nfit_desc *acpi_desc) 
			break;

		}



	queue_delayed_work(nfit_wq, &acpi_desc->dwork, 0);

	sched_ars(acpi_desc);

	return 0;

}
@@ -3241,7 +3263,7 @@ int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, unsigned long flags) 
		}

	}

	if (scheduled) {

		queue_delayed_work(nfit_wq, &acpi_desc->dwork, 0);

		sched_ars(acpi_desc);

		dev_dbg(dev, "ars_scan triggered\n");

	}

	mutex_unlock(&acpi_desc->init_mutex);

drivers/acpi/nfit/nfit.h

+1 −0
Original line number Diff line number Diff line
@@ -203,6 +203,7 @@ struct acpi_nfit_desc { 
	unsigned int max_ars;

	unsigned int scrub_count;

	unsigned int scrub_mode;

	unsigned int scrub_busy:1;

	unsigned int cancel:1;

	unsigned long dimm_cmd_force_en;

	unsigned long bus_cmd_force_en;