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Date:   Mon, 22 Mar 2021 12:42:00 -0400
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Johan Hovold <johan@kernel.org>
Cc:     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>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] USB: ehci: drop workaround for forced irq threading
Message-ID: <20210322164200.GB667925@rowland.harvard.edu>
References: <20210322111249.32141-1-johan@kernel.org>
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On Mon, Mar 22, 2021 at 12:12:49PM +0100, Johan Hovold wrote:
> Force-threaded interrupt handlers used to run with interrupts enabled,
> something which could lead to deadlocks in case a threaded handler
> shared a lock with code running in hard interrupt context (e.g. timer
> callbacks) and did not explicitly disable interrupts.
> 
> Since commit 81e2073c175b ("genirq: Disable interrupts for force
> threaded handlers") interrupt handlers always run with interrupts
> disabled on non-RT so that drivers no longer need to do handle forced
> threading ("threadirqs").

What happens on RT systems?  Are they smart enough to avoid the whole 
problem by enabling interrupts during _all_ callbacks?

Alan Stern