linux-kernel - [PATCH 2/3] venus: core: cancel pending work items in workqueue

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Message-Id: <1596719855-1725-3-git-send-email-mansur@codeaurora.org>
Date:   Thu,  6 Aug 2020 18:47:34 +0530
From:   Mansur Alisha Shaik <mansur@...eaurora.org>
To:     linux-media@...r.kernel.org, stanimir.varbanov@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        vgarodia@...eaurora.org,
        Mansur Alisha Shaik <mansur@...eaurora.org>
Subject: [PATCH 2/3] venus: core: cancel pending work items in workqueue

In concurrency usecase and reboot scenario we are
observing race condition and seeing NULL pointer
dereference crash.when workqueue is in progress
to handle system recovery and at same when device
happends, in bothe paths we are trying to destryo
the same mutex hence seeing the crash.

So this is hadled by protecting hfi_destroy in
remove by mutext variable and cancel a delayed
work items before reboot.

Below is the call trace for the crash
Call trace:
 venus_remove+0xdc/0xec [venus_core]
 venus_core_shutdown+0x1c/0x34 [venus_core]
 platform_drv_shutdown+0x28/0x34
 device_shutdown+0x154/0x1fc
 kernel_restart_prepare+0x40/0x4c
 kernel_restart+0x1c/0x64

Call trace:
 mutex_lock+0x34/0x60
 venus_hfi_destroy+0x28/0x98 [venus_core]
 hfi_destroy+0x1c/0x28 [venus_core]
 venus_sys_error_handler+0x60/0x14c [venus_core]
 process_one_work+0x210/0x3d0
 worker_thread+0x248/0x3f4
 kthread+0x11c/0x12c
 ret_from_fork+0x10/0x18

Signed-off-by: Mansur Alisha Shaik <mansur@...eaurora.org>
---
 drivers/media/platform/qcom/venus/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
index fe99c83..41a293e 100644
--- a/drivers/media/platform/qcom/venus/core.c
+++ b/drivers/media/platform/qcom/venus/core.c
@@ -312,6 +312,8 @@ static int venus_remove(struct platform_device *pdev)
 	struct device *dev = core->dev;
 	int ret;
 
+	cancel_delayed_work_sync(&core->work);
+
 	ret = pm_runtime_get_sync(dev);
 	WARN_ON(ret < 0);
 
@@ -329,7 +331,9 @@ static int venus_remove(struct platform_device *pdev)
 	if (pm_ops->core_put)
 		pm_ops->core_put(dev);
 
+	mutex_lock(&core->lock);
 	hfi_destroy(core);
+	mutex_unlock(&core->lock);
 
 	icc_put(core->video_path);
 	icc_put(core->cpucfg_path);
-- 
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