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@vger.kernel.org Reported-by: Vishal Verma vishal.l.verma@intel.com Tested-by: Vishal Verma vishal.l.verma@intel.com Reported-by: Lukasz Dorau lukasz.dorau@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com --- 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;