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: bc6ba8085842 ("nfit, address-range-scrub: rework and simplify ARS...")
Cc: <stable@xxxxxxxxxxxxxxx>
Reported-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Tested-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Reported-by: Lukasz Dorau <lukasz.dorau@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
Changes in v2:
* Don't touch ->tmo outside of the workqueue itself, it is a private
field for the workqueue to manage. (Vishal)
drivers/acpi/nfit/core.c | 44 +++++++++++++++++++++++++++++++++-----------
drivers/acpi/nfit/nfit.h | 1 +
2 files changed, 34 insertions(+), 11 deletions(-)
diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index 471402cee1f1..b8040fed2a69 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -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);
diff --git a/drivers/acpi/nfit/nfit.h b/drivers/acpi/nfit/nfit.h
index 7d15856a739f..a97ff42fe311 100644
--- a/drivers/acpi/nfit/nfit.h
+++ b/drivers/acpi/nfit/nfit.h
@@ -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;
--
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