linux-kernel - Re: [PATCH] tty: xilinx_uartps: split sysrq handling

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Message-ID: <841px9u5x2.fsf@jogness.linutronix.de>
Date: Sat, 11 Jan 2025 09:16:49 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Sean Anderson <sean.anderson@...ux.dev>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>,
 linux-serial@...r.kernel.org
Cc: Manikanta Guntupalli <manikanta.guntupalli@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Michal
 Simek <michal.simek@....com>, Thomas Gleixner <tglx@...utronix.de>, Sean
 Anderson <sean.anderson@...ux.dev>, stable@...r.kernel.org
Subject: Re: [PATCH] tty: xilinx_uartps: split sysrq handling

On 2025-01-10, Sean Anderson <sean.anderson@...ux.dev> wrote:
> Fix this by splitting sysrq handling into two parts. We use the prepare
> helper under the port lock and defer handling until we release the lock.

Note that this fix is only necessary because this console driver is
using the legacy console API. For the NBCON API it is allowed to call
printk() while holding the port lock.

But since code already exists to allow deferring the sysrq execution
until the port lock is not held, this patch is probably a good idea
anyway because it can reduce port lock contention. AFAIK there are no
sysrq actions that require port lock synchronization.

Acked-by: John Ogness <john.ogness@...utronix.de>