Message-ID: <sashiko-outbox-206190@kernel.org>
From: sashiko-bot@kernel.org
Subject: Re: [PATCH v11 5/8] serial: core: allow drivers to reserve flushed
 transmit storage
Reply-To: sashiko-reviews@lists.linux.dev
To: "James Hilliard" <james.hilliard1@gmail.com>
Cc: linux-serial@vger.kernel.org
In-Reply-To: <20261109-submit-serial-8250-dma-cancel-v1-v11-5-6364edca63d6@gmail.com>
References: <20261109-submit-serial-8250-dma-cancel-v1-v11-0-6364edca63d6@gmail.com>
 <20261109-submit-serial-8250-dma-cancel-v1-v11-5-6364edca63d6@gmail.com>
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Date: Tue, 10 Nov 2026 04:24:03 +0000
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> uart_flush_buffer() resets the transmit FIFO before calling the driver's
> flush callback. An asynchronous DMA transfer can still access that storage
> after the callback returns, while a new write can immediately reuse it.
>=20
> Add uart_xmit_block() and uart_xmit_unblock() so a driver can reserve the
> flushed storage until its transfer and completion callbacks have retired.
> Serialize the reservation with FIFO producers using the port lock.
>=20
> While the storage is reserved, write_room() reports no space and write()
> and put_char() accept no data. Defer write-ready notifications until the
> reservation is released, preserving one-shot TTY wakeups. Keep the flush's
> write-ready notification under the port lock so it cannot race another
> reservation.
>=20
> Wake tty->write_wait after flushing even when writes remain blocked.
> [ ... ]
> Assert the port-lock requirement at uart_write_wakeup(), alongside the
> reservation helpers, so callers cannot inspect readiness or release a
> one-shot notification concurrently with a reservation change.
>=20
> Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

Sashiko has reviewed this patch and found no issues.

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