Cleaning up bf88fef0b6f1 ("usb: otg-fsm: Fix hrtimer list corruption")

Cleaning up bf88fef0b6f1 ("usb: otg-fsm: Fix hrtimer list corruption")

[Oliver Neukum]

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Hi,

I am looking at that patch and I am afraid, while it does the job
it is quite unclean. In effect you introduce a flag you set, but
never clear. That is just a kludge. It really tells you that your
setup of data structures is misplaced and you should just do it earlier.

Could you test the attached patch?

	Regards
		Oliver

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From a11e0684f338f6cf003eb5dfb562d91da1866cc8 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Mon, 29 Aug 2022 14:42:17 +0200
Subject: [PATCH] initialize struct otg_fsm earlier

The earlier fix bf88fef0b6f1 ("usb: otg-fsm: Fix hrtimer list
corruption") in effect hid an issue with intialization.
In effect it replaces the racy continous reinitialization
of fsm->hnp_polling_work with a delayed one-time
initialization.

This just makes no sense. As a single initialization
is sufficient, the clean solution is just to do it once
and do it early enough.

Fixes: bf88fef0b6f1 ("usb: otg-fsm: Fix hrtimer list corruption")
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/common/usb-otg-fsm.c | 7 +------
 drivers/usb/phy/phy-fsl-usb.c    | 1 +
 include/linux/usb/otg-fsm.h      | 1 -
 3 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/common/usb-otg-fsm.c b/drivers/usb/common/usb-otg-fsm.c
index 0697fde51d00..0aa2eb7396ce 100644
--- a/drivers/usb/common/usb-otg-fsm.c
+++ b/drivers/usb/common/usb-otg-fsm.c
@@ -117,7 +117,7 @@ static void otg_leave_state(struct otg_fsm *fsm, enum usb_otg_state old_state)
 	}
 }
 
-static void otg_hnp_polling_work(struct work_struct *work)
+void otg_hnp_polling_work(struct work_struct *work)
 {
 	struct otg_fsm *fsm = container_of(to_delayed_work(work),
 				struct otg_fsm, hnp_polling_work);
@@ -193,11 +193,6 @@ static void otg_start_hnp_polling(struct otg_fsm *fsm)
 	if (!fsm->host_req_flag)
 		return;
 
-	if (!fsm->hnp_work_inited) {
-		INIT_DELAYED_WORK(&fsm->hnp_polling_work, otg_hnp_polling_work);
-		fsm->hnp_work_inited = true;
-	}
-
 	schedule_delayed_work(&fsm->hnp_polling_work,
 					msecs_to_jiffies(T_HOST_REQ_POLL));
 }
diff --git a/drivers/usb/phy/phy-fsl-usb.c b/drivers/usb/phy/phy-fsl-usb.c
index 972704262b02..c3bac7eefe82 100644
--- a/drivers/usb/phy/phy-fsl-usb.c
+++ b/drivers/usb/phy/phy-fsl-usb.c
@@ -844,6 +844,7 @@ int usb_otg_start(struct platform_device *pdev)
 
 	/* Initialize the state machine structure with default values */
 	SET_OTG_STATE(otg_trans, OTG_STATE_UNDEFINED);
+	INIT_DELAYED_WORK(&fsm->hnp_polling_work, otg_hnp_polling_work);
 	fsm->otg = p_otg->phy.otg;
 
 	/* We don't require predefined MEM/IRQ resource index */
diff --git a/include/linux/usb/otg-fsm.h b/include/linux/usb/otg-fsm.h
index 6135d076c53d..cc0bc4edf227 100644
--- a/include/linux/usb/otg-fsm.h
+++ b/include/linux/usb/otg-fsm.h
@@ -183,7 +183,6 @@ struct otg_fsm {
 	struct mutex lock;
 	u8 *host_req_flag;
 	struct delayed_work hnp_polling_work;
-	bool hnp_work_inited;
 	bool state_changed;
 };
 
-- 
2.35.3

Re: Cleaning up bf88fef0b6f1 ("usb: otg-fsm: Fix hrtimer list corruption")

[Dmitry Osipenko]

29.08.2022 16:10, Oliver Neukum пишет:
> Hi,
> 
> I am looking at that patch and I am afraid, while it does the job
> it is quite unclean. In effect you introduce a flag you set, but
> never clear. That is just a kludge. It really tells you that your
> setup of data structures is misplaced and you should just do it earlier.
> 
> Could you test the attached patch?
> 
> 	Regards
> 		Oliver

That certainly won't work because phy-fsl has nothing to do with the
original problem. You'll need to check carefully every USB controller
driver. It's just not very worthwhile to do, IMO.