[PATCH -v1] acpi: Fix possible recursive locking in hwregs.c

[Rakib Mullick]

Calling pm-suspend might trigger a recursive lock in it's code path. In function acpi_hw_clear_acpi_status, 
acpi_os_acquire_lock holds the lock acpi_gbl_hardware_lock before calling acpi_hw_register_write(), then 
without releasing acpi_gbl_hardware_lock, this function calls acpi_ev_walk_gpe_list, which tries to hold 
acpi_gbl_gpe_lock and thus might causes possible recursive lock.

Following patch fixes this scenario by just releasing acpi_gbl_hardware_lock before calling acpi_ev_walk_gpe_list.

 Changes since v0(https://lkml.org/lkml/2011/9/21/355):
	- Fix changelog, thanks to Lin Ming.

Signed-off-by: Rakib Mullick <rakib.mullick@xxxxxxxxx>
Cc: Lin Ming <ming.m.lin@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
---

diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
index 55accb7..e3110ac 100644
--- a/drivers/acpi/acpica/hwregs.c
+++ b/drivers/acpi/acpica/hwregs.c
@@ -269,6 +269,9 @@ acpi_status acpi_hw_clear_acpi_status(void)
 
 	status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS,
 					ACPI_BITMASK_ALL_FIXED_STATUS);
+
+	acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
+
 	if (ACPI_FAILURE(status)) {
 		goto unlock_and_exit;
 	}
@@ -278,7 +281,6 @@ acpi_status acpi_hw_clear_acpi_status(void)
 	status = acpi_ev_walk_gpe_list(acpi_hw_clear_gpe_block, NULL);
 
       unlock_and_exit:
-	acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
 	return_ACPI_STATUS(status);
 }
 


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