From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: Re: [PATCH -v2] acpi: Fix possible recursive locking in hwregs.c Date: Mon, 07 Nov 2011 01:16:30 +0530 Message-ID: <4EB6E416.4080201@linux.vnet.ibm.com> References: <1320592697.7439.3.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from e23smtp02.au.ibm.com ([202.81.31.144]:45674 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751087Ab1KFTqt (ORCPT ); Sun, 6 Nov 2011 14:46:49 -0500 In-Reply-To: <1320592697.7439.3.camel@localhost.localdomain> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Rakib Mullick Cc: linux-kernel , linux-acpi , akpm@linux-foundation.org, ming Lin , len.brown@intel.com On 11/06/2011 08:48 PM, Rakib Mullick wrote: > 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. Both acpi_gbl_hardware_lock and acpi_gbl_gpe_lock are at same lock-class and which might cause lock recursion deadlock. > > 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. > > Changes since v1 (https://lkml.org/lkml/2011/11/3/89): > - Update changelog and rename goto label, courtesy Srivatsa S. Bhat. > > Signed-off-by: Rakib Mullick > Cc: Lin Ming > Cc: Andrew Morton > Cc: Len Brown > Cc: Srivatsa S. Bhat > --- > It would be a good idea to also give the lockdep warning in the changelog (though you triggered it in a modified kernel), since that would make it very clear as to what problem your patch is trying to solve. [And please line-wrap your changelog to 80 characters at most, per line]. Code-wise, the patch looks good to me. So, Reviewed-by: Srivatsa S. Bhat Thanks, Srivatsa S. Bhat > diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c > index 55accb7..cc70f3f 100644 > --- a/drivers/acpi/acpica/hwregs.c > +++ b/drivers/acpi/acpica/hwregs.c > @@ -269,16 +269,17 @@ acpi_status acpi_hw_clear_acpi_status(void) > > status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS, > ACPI_BITMASK_ALL_FIXED_STATUS); > - if (ACPI_FAILURE(status)) { > - goto unlock_and_exit; > - } > + > + acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags); > + > + if (ACPI_FAILURE(status)) > + goto exit; > > /* Clear the GPE Bits in all GPE registers in all GPE blocks */ > > 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); > +exit: > return_ACPI_STATUS(status); > } > > >