-----Original Message----- From: Thomas Renninger [mailto:[email protected]] Sent: Friday, October 08, 2010 3:40 AM To: Moore, Robert; ACPI Devel Maling List Cc: devel(a)acpica.org; stuart_hayes(a)dell.com Subject: [PATCH] ACPICA: Do not hang at mutex forever if BIOS tries to release global lock Hi, find the code against the Linux kernel pasted at the end of the mail for review. Find the code adjusted for ACPICA inclusion in the attachement. Bob: If you are ok with the patch, it would be great if you could push it. Be aware that I did not compile tested it in ACPICA environment. Thanks, Thomas From: Stuart Hayes <stuart_hayes(a)dell.com&gt; ACPICA: Do not hang at mutex forever if BIOS tries to release global lock and OS did not request the lock (means the pending bit was not set). Which in fact is a BIOS/HW bug (compare with ACPI Spec 3.0b): 5.2.10.1 Global Lock: .. This signal only occurs when the other environment attempted to acquire ownership while the lock was owned. .. or 4.7.3.1.1 PM1 Status Registers GBL_STS: .. This bit is set in response to the BIOS releasing control of the Global Lock and having seen the pending bit set. .. There seem to be chipsets which can get this wrong (especially after a kexec boot on Linux). Also one could theoretically run into this if a new kernel got booted without proper reboot and BIOS re-initialization (like kexec) while: 1) The OS hold the global lock 2) The BIOS hold the global lock This patch would handle condition 1. To make sure condition 2. cannot happen, it should get stated in the ACPI spec that the global lock needs to be zeroed by BIOS everytime the OS tries to (re-)enable ACPI mode. Modifications by trenn: - Add a message -> This should not happen and if it happens it should not be ignored/handled silently - Adjusted from Linux kernel to acpica sources Signed-off-by: Thomas Renninger <trenn(a)suse.de&gt; diff -purN '--exclude=*orig' linux-2.6.36- rc6_orig/drivers/acpi/acpica/acglobal.h linux-2.6.36- rc6/drivers/acpi/acpica/acglobal.h --- linux-2.6.36-rc6_orig/drivers/acpi/acpica/acglobal.h 2010-06-02 09:16:14.000000000 -0500 +++ linux-2.6.36-rc6/drivers/acpi/acpica/acglobal.h 2010-06-02 09:24:44.000000000 -0500 @@ -213,6 +213,7 @@ ACPI_EXTERN acpi_semaphore acpi_gbl_glob ACPI_EXTERN u16 acpi_gbl_global_lock_handle; ACPI_EXTERN u8 acpi_gbl_global_lock_acquired; ACPI_EXTERN u8 acpi_gbl_global_lock_present; +ACPI_EXTERN u32 acpi_gbl_global_lock_pending; /* * Spinlocks are used for interfaces that can be possibly called at diff -purN '--exclude=*orig' linux-2.6.36- rc6_orig/drivers/acpi/acpica/evmisc.c linux-2.6.36- rc6/drivers/acpi/acpica/evmisc.c --- linux-2.6.36-rc6_orig/drivers/acpi/acpica/evmisc.c 2010-06-02 09:16:11.000000000 -0500 +++ linux-2.6.36-rc6/drivers/acpi/acpica/evmisc.c 2010-06-02 09:24:45.000000000 -0500 @@ -297,6 +297,17 @@ static u32 acpi_ev_global_lock_handler(v { u8 acquired = FALSE; + /* This must not happen: BIOS must only release the lock if OS has set + * it pending. Such inconsistancies could happen if the global lock bits + * survived through a kexec boot. */ + + if (!acpi_gbl_global_lock_pending) { + u8 pending; + /* Clear lock bits. BIOS released lock and OS isn't waiting. */ + ACPI_RELEASE_GLOBAL_LOCK(acpi_gbl_FACS, pending); + return (ACPI_INTERRUPT_HANDLED); + } + /* * Attempt to get the lock. * @@ -309,6 +320,7 @@ static u32 acpi_ev_global_lock_handler(v /* Got the lock, now wake all threads waiting for it */ acpi_gbl_global_lock_acquired = TRUE; + acpi_gbl_global_lock_pending--; /* Send a unit to the semaphore */ if (ACPI_FAILURE @@ -479,6 +491,8 @@ acpi_status acpi_ev_acquire_global_lock( acpi_gbl_global_lock_acquired = TRUE; return_ACPI_STATUS(AE_OK); + } else { + acpi_gbl_global_lock_pending++; } /* diff -purN '--exclude=*orig' linux-2.6.36- rc6_orig/drivers/acpi/acpica/utglobal.c linux-2.6.36- rc6/drivers/acpi/acpica/utglobal.c --- linux-2.6.36-rc6_orig/drivers/acpi/acpica/utglobal.c 2010-06-02 09:16:14.000000000 -0500 +++ linux-2.6.36-rc6/drivers/acpi/acpica/utglobal.c 2010-06-02 09:24:45.000000000 -0500 @@ -782,6 +782,7 @@ acpi_status acpi_ut_init_globals(void) acpi_gbl_global_lock_acquired = FALSE; acpi_gbl_global_lock_handle = 0; acpi_gbl_global_lock_present = FALSE; + acpi_gbl_global_lock_pending = 0; /* Miscellaneous variables */