From: Alan Stern <stern@rowland.harvard.edu>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Johan Hovold <johan@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
Stanislaw Gruszka <sgruszka@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] USB: ehci: drop workaround for forced irq threading
Date: Mon, 22 Mar 2021 15:01:25 -0400 [thread overview]
Message-ID: <20210322190125.GD675969@rowland.harvard.edu> (raw)
In-Reply-To: <20210322165917.it5d5f5kuvs7jah5@linutronix.de>
On Mon, Mar 22, 2021 at 05:59:17PM +0100, Sebastian Andrzej Siewior wrote:
> On 2021-03-22 12:42:00 [-0400], Alan Stern wrote:
> > What happens on RT systems? Are they smart enough to avoid the whole
> > problem by enabling interrupts during _all_ callbacks?
>
> tl;dr: Yes.
>
> The referenced commit (id 81e2073c175b) disables interrupts only on !RT
> configs so for RT everything remains unchanged (the backports are
> already adjusted for the old stable trees to use the proper CONFIG_* for
> enabled RT).
>
> All hrtimer callbacks run as HRTIMER_MODE_SOFT by default. The
> HRTIMER_MODE_HARD ones (which expire in HARDIRQ context) were audited /
> explicitly enabled.
> The same goes irq_work.
> The printk code is different compared to mainline. A printk() on RT in
> HARDIRQ context is printed once the HARDIRQ context is left. So the
> serial/console/… driver never gets a chance to acquire its lock in
> hardirq context.
>
> An interrupt handler which is not forced-threaded must be marked as such
> and must not use any spinlock_t based locking. lockdep/might_sleep
> complain here already.
Okay, in that case:
Acked-by: Alan Stern <stern@rowland.harvard.edu>
prev parent reply other threads:[~2021-03-22 19:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 11:12 [PATCH] USB: ehci: drop workaround for forced irq threading Johan Hovold
2021-03-22 16:42 ` Alan Stern
2021-03-22 16:59 ` Sebastian Andrzej Siewior
2021-03-22 19:01 ` Alan Stern [this message]
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