[PATCH v2] ACPI: sleep: Avoid breaking S3 wakeup due to might_sleep()

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

The addition of might_sleep() to down_timeout() caused the latter to
enable interrupts unconditionally in some cases, which in turn broke
the ACPI S3 wakeup path in acpi_suspend_enter(), where down_timeout()
is called by acpi_disable_all_gpes() via acpi_ut_acquire_mutex().

Namely, if CONFIG_DEBUG_ATOMIC_SLEEP is set, might_sleep() causes
might_resched() to be used and if CONFIG_PREEMPT_VOLUNTARY is set,
this triggers __cond_resched() which may call preempt_schedule_common(),
so __schedule() gets invoked and it ends up with enabled interrupts (in
the prev == next case).

Now, enabling interrupts early in the S3 wakeup path causes the kernel
to crash.

Address this by modifying acpi_suspend_enter() to disable GPEs without
attempting to acquire the sleeping lock which is not needed in that code
path anyway.

Fixes: 99409b935c9a ("locking/semaphore: Add might_sleep() to down_*() family")
Reported-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---

v1 -> v2:
   * Rephrase the comment in acpi_suspend_enter() (Peter)
   * Fix up the Fixes tag (Peter)
   * Add Peter's ACK

---
 drivers/acpi/acpica/achware.h |    2 --
 drivers/acpi/sleep.c          |   16 ++++++++++++----
 include/acpi/acpixf.h         |    1 +
 3 files changed, 13 insertions(+), 6 deletions(-)

Index: linux-pm/drivers/acpi/acpica/achware.h
===================================================================
--- linux-pm.orig/drivers/acpi/acpica/achware.h
+++ linux-pm/drivers/acpi/acpica/achware.h
@@ -101,8 +101,6 @@ acpi_status
 acpi_hw_get_gpe_status(struct acpi_gpe_event_info *gpe_event_info,
 		       acpi_event_status *event_status);
 
-acpi_status acpi_hw_disable_all_gpes(void);
-
 acpi_status acpi_hw_enable_all_runtime_gpes(void);
 
 acpi_status acpi_hw_enable_all_wakeup_gpes(void);
Index: linux-pm/include/acpi/acpixf.h
===================================================================
--- linux-pm.orig/include/acpi/acpixf.h
+++ linux-pm/include/acpi/acpixf.h
@@ -761,6 +761,7 @@ ACPI_HW_DEPENDENT_RETURN_STATUS(acpi_sta
 						     acpi_event_status
 						     *event_status))
 ACPI_HW_DEPENDENT_RETURN_UINT32(u32 acpi_dispatch_gpe(acpi_handle gpe_device, u32 gpe_number))
+ACPI_HW_DEPENDENT_RETURN_STATUS(acpi_status acpi_hw_disable_all_gpes(void))
 ACPI_HW_DEPENDENT_RETURN_STATUS(acpi_status acpi_disable_all_gpes(void))
 ACPI_HW_DEPENDENT_RETURN_STATUS(acpi_status acpi_enable_all_runtime_gpes(void))
 ACPI_HW_DEPENDENT_RETURN_STATUS(acpi_status acpi_enable_all_wakeup_gpes(void))
Index: linux-pm/drivers/acpi/sleep.c
===================================================================
--- linux-pm.orig/drivers/acpi/sleep.c
+++ linux-pm/drivers/acpi/sleep.c
@@ -636,11 +636,19 @@ static int acpi_suspend_enter(suspend_st
 	}
 
 	/*
-	 * Disable and clear GPE status before interrupt is enabled. Some GPEs
-	 * (like wakeup GPE) haven't handler, this can avoid such GPE misfire.
-	 * acpi_leave_sleep_state will reenable specific GPEs later
+	 * Disable all GPE and clear their status bits before interrupts are
+	 * enabled. Some GPEs (like wakeup GPEs) have no handlers and this can
+	 * prevent them from producing spurious interrups.
+	 *
+	 * acpi_leave_sleep_state() will reenable specific GPEs later.
+	 *
+	 * Because this code runs on one CPU with disabled interrupts (all of
+	 * the other CPUs are offline at this time), it need not acquire any
+	 * sleeping locks which may trigger an implicit preemption point even
+	 * if there is no contention, so avoid doing that by using a low-level
+	 * library routine here.
 	 */
-	acpi_disable_all_gpes();
+	acpi_hw_disable_all_gpes();
 	/* Allow EC transactions to happen. */
 	acpi_ec_unblock_transactions();