Patch "[media] s5p-mfc: Fix race between interrupt routine and device functions" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

[media] s5p-mfc: Fix race between interrupt routine and device functions

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
s5p-mfc-fix-race-between-interrupt-routine-and-device-functions.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Marek Szyprowski <[email protected]>
Date: Thu, 23 Feb 2017 08:43:27 -0300
Subject: [media] s5p-mfc: Fix race between interrupt routine and device functions

From: Marek Szyprowski <[email protected]>

commit 0c32b8ec02832df167e16ad659cb11dc148f2ddf upstream.

Interrupt routine must wake process waiting for given interrupt AFTER updating driver's internal structures and contexts. Doing it in-between is a serious bug. This patch moves all calls to the wake() function to the end of the interrupt processing block to avoid potential and real races, especially on multi-core platforms. This also fixes following issue reported from clock core (clocks were disabled in interrupt after being unprepared from the other place in the driver, the stack trace however points to the different place than s5p_mfc driver because of the race):

WARNING: CPU: 1 PID: 18 at drivers/clk/clk.c:544 clk_core_unprepare+0xc8/0x108
Modules linked in:
CPU: 1 PID: 18 Comm: kworker/1:0 Not tainted 4.10.0-next-20170223-00070-g04e18bc99ab9-dirty #2154
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
Workqueue: pm pm_runtime_work
[<c010d8b0>] (unwind_backtrace) from [<c010a534>] (show_stack+0x10/0x14)
[<c010a534>] (show_stack) from [<c033292c>] (dump_stack+0x74/0x94)
[<c033292c>] (dump_stack) from [<c011cef4>] (__warn+0xd4/0x100)
[<c011cef4>] (__warn) from [<c011cf40>] (warn_slowpath_null+0x20/0x28)
[<c011cf40>] (warn_slowpath_null) from [<c0387a84>] (clk_core_unprepare+0xc8/0x108)
[<c0387a84>] (clk_core_unprepare) from [<c0389d84>] (clk_unprepare+0x24/0x2c)
[<c0389d84>] (clk_unprepare) from [<c03d4660>] (exynos_sysmmu_suspend+0x48/0x60)
[<c03d4660>] (exynos_sysmmu_suspend) from [<c042b9b0>] (pm_generic_runtime_suspend+0x2c/0x38)
[<c042b9b0>] (pm_generic_runtime_suspend) from [<c0437580>] (genpd_runtime_suspend+0x94/0x220)
[<c0437580>] (genpd_runtime_suspend) from [<c042e240>] (__rpm_callback+0x134/0x208)
[<c042e240>] (__rpm_callback) from [<c042e334>] (rpm_callback+0x20/0x80)
[<c042e334>] (rpm_callback) from [<c042d3b8>] (rpm_suspend+0xdc/0x458)
[<c042d3b8>] (rpm_suspend) from [<c042ea24>] (pm_runtime_work+0x80/0x90)
[<c042ea24>] (pm_runtime_work) from [<c01322c4>] (process_one_work+0x120/0x318)
[<c01322c4>] (process_one_work) from [<c0132520>] (worker_thread+0x2c/0x4ac)
[<c0132520>] (worker_thread) from [<c0137ab0>] (kthread+0xfc/0x134)
[<c0137ab0>] (kthread) from [<c0107978>] (ret_from_fork+0x14/0x3c)
---[ end trace 1ead49a7bb83f0d8 ]---

---
 drivers/media/platform/s5p-mfc/s5p_mfc.c |   12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

@@ -663,9 +663,9 @@ static irqreturn_t s5p_mfc_irq(int irq,
 				break;
 			}
 			s5p_mfc_hw_call(dev->mfc_ops, clear_int_flags, dev);
-			wake_up_ctx(ctx, reason, err);
 			WARN_ON(test_and_clear_bit(0, &dev->hw_lock) == 0);
 			s5p_mfc_clock_off();
+			wake_up_ctx(ctx, reason, err);
 			s5p_mfc_hw_call(dev->mfc_ops, try_run, dev);
 		} else {
 			s5p_mfc_handle_frame(ctx, reason, err);

@@ -679,15 +679,11 @@ static irqreturn_t s5p_mfc_irq(int irq,
 	case S5P_MFC_R2H_CMD_OPEN_INSTANCE_RET:
 		ctx->inst_no = s5p_mfc_hw_call(dev->mfc_ops, get_inst_no, dev);
 		ctx->state = MFCINST_GOT_INST;
-		clear_work_bit(ctx);
-		wake_up(&ctx->queue);
 		goto irq_cleanup_hw;
 
 	case S5P_MFC_R2H_CMD_CLOSE_INSTANCE_RET:
-		clear_work_bit(ctx);
 		ctx->inst_no = MFC_NO_INSTANCE_SET;
 		ctx->state = MFCINST_FREE;
-		wake_up(&ctx->queue);
 		goto irq_cleanup_hw;
 
 	case S5P_MFC_R2H_CMD_SYS_INIT_RET:

@@ -697,9 +693,9 @@ static irqreturn_t s5p_mfc_irq(int irq,
 		if (ctx)
 			clear_work_bit(ctx);
 		s5p_mfc_hw_call(dev->mfc_ops, clear_int_flags, dev);
-		wake_up_dev(dev, reason, err);
 		clear_bit(0, &dev->hw_lock);
 		clear_bit(0, &dev->enter_suspend);
+		wake_up_dev(dev, reason, err);
 		break;
 
 	case S5P_MFC_R2H_CMD_INIT_BUFFERS_RET:

@@ -714,9 +710,7 @@ static irqreturn_t s5p_mfc_irq(int irq,
 		break;
 
 	case S5P_MFC_R2H_CMD_DPB_FLUSH_RET:
-		clear_work_bit(ctx);
 		ctx->state = MFCINST_RUNNING;
-		wake_up(&ctx->queue);
 		goto irq_cleanup_hw;
 
 	default:

@@ -735,6 +729,8 @@ irq_cleanup_hw:
 		mfc_err("Failed to unlock hw\n");
 
 	s5p_mfc_clock_off();
+	clear_work_bit(ctx);
+	wake_up(&ctx->queue);
 
 	s5p_mfc_hw_call(dev->mfc_ops, try_run, dev);
 	spin_unlock(&dev->irqlock);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/s5p-mfc-fix-race-between-interrupt-routine-and-device-functions.patch queue-4.9/s5p-mfc-fix-unbalanced-call-to-clock-management.patch