From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7C6C296BCC; Sun, 7 Jun 2026 10:45:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780829152; cv=none; b=glao5ev00J6EYLURbE9pWlviCrpOsgyVvcsxYbsLEW5OlfJjUjBbIIJpGTgDRgkx710SBQbqzOgT8Oloaki/ueHNiRSpikFT4FGPs91IkjYyzHow+abUJkp4ewrE4jIeQCWeaDuRY0eNMjSE10nl0hwP7kVv0LE4GQKgnGdrLsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780829152; c=relaxed/simple; bh=c0KMqEgJ3n2SnXQQCsH/Eb+IhnTCnC1Dec0welORJ3M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Q0FKURXE3CcZf9mXxSbt+XLKjdioZAp4rz4Yspm/njpc6jL/XoG23KwTvTBji5TezmlnK+I98A41fnkx4mp/N2fXg7wdb8Zk3PKNUwrcKRGkd9AgaSNdg7nZozu0oIYfuYWwVGhvE3KsSK47BOKq0rZqP811fBaOmkzuyl2kPU4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xG9DQqK5; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xG9DQqK5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D96801F00893; Sun, 7 Jun 2026 10:45:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780829151; bh=nqq7L5WOCh1MCzg8neTLrIjND1CrziPI2wZwStVJOFI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=xG9DQqK5FAv+YooaZkKRpM2Zl9omuuQSeSGtZJvBc3TRnBhHgG5JcyLdG+NdKXThG hQA8Gkj9APDokGD++p0avNLPu0+0XfW2ovL6Chy8WNPpposCsOflQQoAeUPbrnjAh4 Y+2dzJVxuLO0uLS1Jc14WPtcpkRLAD2+hB+tywuI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , John Ogness , Tudor Ambarus Subject: [PATCH 6.18 221/315] tty: serial: samsung: Remove redundant port lock acquisition in rx helpers Date: Sun, 7 Jun 2026 12:00:08 +0200 Message-ID: <20260607095735.693942145@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260607095727.528828913@linuxfoundation.org> References: <20260607095727.528828913@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tudor Ambarus commit a3bb136bff5e6a5e48cdd813246c9c4686feaaa9 upstream. Sashiko identified a deadlock when the console flow is engaged [1]. When console flow control is enabled (UPF_CONS_FLOW), s3c24xx_serial_stop_tx() calls s3c24xx_serial_rx_enable() and s3c24xx_serial_start_tx() calls s3c24xx_serial_rx_disable(). The serial core framework invokes the .stop_tx() and .start_tx() callbacks with the port->lock spinlock already held. Furthermore, all internal driver paths that invoke stop_tx (such as the DMA TX completion handler s3c24xx_serial_tx_dma_complete() or the PIO TX IRQ handler s3c24xx_serial_tx_irq()) also acquire port->lock prior to calling it. (Note that s3c24xx_serial_start_tx() is only invoked by the serial core). However, s3c24xx_serial_rx_enable() and s3c24xx_serial_rx_disable() unconditionally attempt to acquire port->lock again using uart_port_lock_irqsave(). Since spinlocks are not recursive, this causes a deadlock on the same CPU when console flow control is engaged. Remove the redundant lock acquisition from both rx helper functions. Cc: stable Fixes: b497549a035c ("[ARM] S3C24XX: Split serial driver into core and per-cpu drivers") Reported-by: John Ogness Closes: https://sashiko.dev/#/patchset/20260506121606.5805-1-john.ogness%40linutronix.de [1] Signed-off-by: Tudor Ambarus Link: https://patch.msgid.link/20260515-samsung-tty-flow-control-deadlock-v1-1-93255edbc9bc@linaro.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/samsung_tty.c | 8 -------- 1 file changed, 8 deletions(-) --- a/drivers/tty/serial/samsung_tty.c +++ b/drivers/tty/serial/samsung_tty.c @@ -245,12 +245,9 @@ static bool s3c24xx_serial_txempty_nofif static void s3c24xx_serial_rx_enable(struct uart_port *port) { struct s3c24xx_uart_port *ourport = to_ourport(port); - unsigned long flags; int count = 10000; u32 ucon, ufcon; - uart_port_lock_irqsave(port, &flags); - while (--count && !s3c24xx_serial_txempty_nofifo(port)) udelay(100); @@ -263,23 +260,18 @@ static void s3c24xx_serial_rx_enable(str wr_regl(port, S3C2410_UCON, ucon); ourport->rx_enabled = 1; - uart_port_unlock_irqrestore(port, flags); } static void s3c24xx_serial_rx_disable(struct uart_port *port) { struct s3c24xx_uart_port *ourport = to_ourport(port); - unsigned long flags; u32 ucon; - uart_port_lock_irqsave(port, &flags); - ucon = rd_regl(port, S3C2410_UCON); ucon &= ~S3C2410_UCON_RXIRQMODE; wr_regl(port, S3C2410_UCON, ucon); ourport->rx_enabled = 0; - uart_port_unlock_irqrestore(port, flags); } static void s3c24xx_serial_stop_tx(struct uart_port *port)