linux-kernel - Re: [PATCH] kcov, usb: Fix invalid context sleep in softirq path on PREEMPT

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Message-ID: <20250811083135.xtl2wSQz@linutronix.de>
Date: Mon, 11 Aug 2025 10:31:35 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Yunseong Kim <ysk@...lloc.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Byungchul Park <byungchul@...com>, max.byungchul.park@...il.com,
	Yeoreum Yun <yeoreum.yun@....com>,
	Michelle Jin <shjy180909@...il.com>, linux-kernel@...r.kernel.org,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Thomas Gleixner <tglx@...utronix.de>, stable@...r.kernel.org,
	kasan-dev@...glegroups.com, syzkaller@...glegroups.com,
	linux-usb@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	Austin Kim <austindh.kim@...il.com>
Subject: Re: [PATCH] kcov, usb: Fix invalid context sleep in softirq path on
 PREEMPT_RT

On 2025-08-09 02:35:48 [+0900], Yunseong Kim wrote:
> Hi Sebastian,
Hi Yunseong,

> > Could someone maybe test this?
> 
> As you requested, I have tested your patch on my setup.
> 
> I can check that your patch resolves the issue. I have been running
> the syzkaller for several hours, and the "sleeping function called
> from invalid context" bug is no longer triggered.

Thank you. I just sent this as a proper patch assuming kcov still does
what it should. I just don't understand why this triggers after moving
to workqueues and did not with the tasklet setup. Other that than
workqueue code has a bit more overhead, it is the same thing.

> I really impressed your "How to Not Break PREEMPT_RT" talk at LPC 22.

Thank you.

> 
> Tested-by: Yunseong Kim <ysk@...lloc.com>
> 
> 
> Thanks,
> 
> Yunseong Kim

Sebastian