diff mbox series

[v2,18/23] PM / QoS: Decouple request alloc from dev_pm_qos_mtx

Message ID 20230320144356.803762-19-robdclark@gmail.com
State New
Headers show
Series drm/msm+PM+icc: Make job_run() reclaim-safe | expand

Commit Message

Rob Clark March 20, 2023, 2:43 p.m. UTC 
From: Rob Clark <robdclark@chromium.org>

Similar to the previous patch, move the allocation out from under
dev_pm_qos_mtx, by speculatively doing the allocation and handle
any race after acquiring dev_pm_qos_mtx by freeing the redundant
allocation.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/base/power/qos.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Comments

kernel test robot March 20, 2023, 8:34 p.m. UTC | #1 
Hi Rob,

I love your patch! Perhaps something to improve:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on rafael-pm/linux-next drm-intel/for-linux-next drm-intel/for-linux-next-fixes drm-tip/drm-tip linus/master v6.3-rc3 next-20230320]
[cannot apply to chanwoo/devfreq-testing]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Rob-Clark/drm-msm-Pre-allocate-hw_fence/20230320-224826
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230320144356.803762-19-robdclark%40gmail.com
patch subject: [PATCH v2 18/23] PM / QoS: Decouple request alloc from dev_pm_qos_mtx
config: x86_64-randconfig-a014 (https://download.01.org/0day-ci/archive/20230321/202303210420.9g2z6MgO-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/2d7e4629d7265d7e77fc72d01e84d27d805b7485
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Rob-Clark/drm-msm-Pre-allocate-hw_fence/20230320-224826
        git checkout 2d7e4629d7265d7e77fc72d01e84d27d805b7485
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/base/power/ drivers/char/tpm/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303210420.9g2z6MgO-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/base/power/qos.c:947:8: warning: variable 'req' is uninitialized when used here [-Wuninitialized]
                   if (!req) {
                        ^~~
   drivers/base/power/qos.c:938:33: note: initialize the variable 'req' to silence this warning
                   struct dev_pm_qos_request *req;
                                                 ^
                                                  = NULL
   1 warning generated.


vim +/req +947 drivers/base/power/qos.c

2d984ad132a87c Rafael J. Wysocki 2014-02-11  917  
2d984ad132a87c Rafael J. Wysocki 2014-02-11  918  /**
2d984ad132a87c Rafael J. Wysocki 2014-02-11  919   * dev_pm_qos_update_user_latency_tolerance - Update user space latency tolerance.
2d984ad132a87c Rafael J. Wysocki 2014-02-11  920   * @dev: Device to update the user space latency tolerance for.
2d984ad132a87c Rafael J. Wysocki 2014-02-11  921   * @val: New user space latency tolerance for @dev (negative values disable).
2d984ad132a87c Rafael J. Wysocki 2014-02-11  922   */
2d984ad132a87c Rafael J. Wysocki 2014-02-11  923  int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
2d984ad132a87c Rafael J. Wysocki 2014-02-11  924  {
2d7e4629d7265d Rob Clark         2023-03-20  925  	struct dev_pm_qos_request *req = NULL;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  926  	int ret;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  927  
00dd582e52a535 Rob Clark         2023-03-20  928  	ret = dev_pm_qos_constraints_ensure_allocated(dev);
00dd582e52a535 Rob Clark         2023-03-20  929  	if (ret)
00dd582e52a535 Rob Clark         2023-03-20  930  		return ret;
00dd582e52a535 Rob Clark         2023-03-20  931  
2d7e4629d7265d Rob Clark         2023-03-20  932  	if (!dev->power.qos->latency_tolerance_req)
2d7e4629d7265d Rob Clark         2023-03-20  933  		req = kzalloc(sizeof(*req), GFP_KERNEL);
2d7e4629d7265d Rob Clark         2023-03-20  934  
2d984ad132a87c Rafael J. Wysocki 2014-02-11  935  	mutex_lock(&dev_pm_qos_mtx);
2d984ad132a87c Rafael J. Wysocki 2014-02-11  936  
00dd582e52a535 Rob Clark         2023-03-20  937  	if (!dev->power.qos->latency_tolerance_req) {
2d984ad132a87c Rafael J. Wysocki 2014-02-11  938  		struct dev_pm_qos_request *req;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  939  
2d984ad132a87c Rafael J. Wysocki 2014-02-11  940  		if (val < 0) {
80a6f7c79b7822 Andrew Lutomirski 2016-11-29  941  			if (val == PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT)
80a6f7c79b7822 Andrew Lutomirski 2016-11-29  942  				ret = 0;
80a6f7c79b7822 Andrew Lutomirski 2016-11-29  943  			else
2d984ad132a87c Rafael J. Wysocki 2014-02-11  944  				ret = -EINVAL;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  945  			goto out;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  946  		}
2d984ad132a87c Rafael J. Wysocki 2014-02-11 @947  		if (!req) {
2d984ad132a87c Rafael J. Wysocki 2014-02-11  948  			ret = -ENOMEM;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  949  			goto out;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  950  		}
2d984ad132a87c Rafael J. Wysocki 2014-02-11  951  		ret = __dev_pm_qos_add_request(dev, req, DEV_PM_QOS_LATENCY_TOLERANCE, val);
2d984ad132a87c Rafael J. Wysocki 2014-02-11  952  		if (ret < 0) {
2d984ad132a87c Rafael J. Wysocki 2014-02-11  953  			kfree(req);
2d984ad132a87c Rafael J. Wysocki 2014-02-11  954  			goto out;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  955  		}
2d984ad132a87c Rafael J. Wysocki 2014-02-11  956  		dev->power.qos->latency_tolerance_req = req;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  957  	} else {
2d7e4629d7265d Rob Clark         2023-03-20  958  		/*
2d7e4629d7265d Rob Clark         2023-03-20  959  		 * If we raced with another thread to allocate the request,
2d7e4629d7265d Rob Clark         2023-03-20  960  		 * simply free the redundant allocation and move on.
2d7e4629d7265d Rob Clark         2023-03-20  961  		 */
2d7e4629d7265d Rob Clark         2023-03-20  962  		if (req)
2d7e4629d7265d Rob Clark         2023-03-20  963  			kfree(req);
2d7e4629d7265d Rob Clark         2023-03-20  964  
2d984ad132a87c Rafael J. Wysocki 2014-02-11  965  		if (val < 0) {
2d984ad132a87c Rafael J. Wysocki 2014-02-11  966  			__dev_pm_qos_drop_user_request(dev, DEV_PM_QOS_LATENCY_TOLERANCE);
2d984ad132a87c Rafael J. Wysocki 2014-02-11  967  			ret = 0;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  968  		} else {
2d984ad132a87c Rafael J. Wysocki 2014-02-11  969  			ret = __dev_pm_qos_update_request(dev->power.qos->latency_tolerance_req, val);
2d984ad132a87c Rafael J. Wysocki 2014-02-11  970  		}
2d984ad132a87c Rafael J. Wysocki 2014-02-11  971  	}
2d984ad132a87c Rafael J. Wysocki 2014-02-11  972  
2d984ad132a87c Rafael J. Wysocki 2014-02-11  973   out:
2d984ad132a87c Rafael J. Wysocki 2014-02-11  974  	mutex_unlock(&dev_pm_qos_mtx);
2d984ad132a87c Rafael J. Wysocki 2014-02-11  975  	return ret;
2d984ad132a87c Rafael J. Wysocki 2014-02-11  976  }
034e7906211c18 Andrew Lutomirski 2016-11-29  977  EXPORT_SYMBOL_GPL(dev_pm_qos_update_user_latency_tolerance);
13b2c4a0c3b1cd Mika Westerberg   2015-07-27  978
diff mbox series

Patch

diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index f3e0c6b65635..9cba334b3729 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -922,12 +922,16 @@  s32 dev_pm_qos_get_user_latency_tolerance(struct device *dev)
  */
 int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
 {
+	struct dev_pm_qos_request *req = NULL;
 	int ret;
 
 	ret = dev_pm_qos_constraints_ensure_allocated(dev);
 	if (ret)
 		return ret;
 
+	if (!dev->power.qos->latency_tolerance_req)
+		req = kzalloc(sizeof(*req), GFP_KERNEL);
+
 	mutex_lock(&dev_pm_qos_mtx);
 
 	if (!dev->power.qos->latency_tolerance_req) {
@@ -940,7 +944,6 @@  int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
 				ret = -EINVAL;
 			goto out;
 		}
-		req = kzalloc(sizeof(*req), GFP_KERNEL);
 		if (!req) {
 			ret = -ENOMEM;
 			goto out;
@@ -952,6 +955,13 @@  int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
 		}
 		dev->power.qos->latency_tolerance_req = req;
 	} else {
+		/*
+		 * If we raced with another thread to allocate the request,
+		 * simply free the redundant allocation and move on.
+		 */
+		if (req)
+			kfree(req);
+
 		if (val < 0) {
 			__dev_pm_qos_drop_user_request(dev, DEV_PM_QOS_LATENCY_TOLERANCE);
 			ret = 0;