From patchwork Tue Aug 20 06:29:40 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Ogness X-Patchwork-Id: 820903 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 0E1741E212E; Tue, 20 Aug 2024 06:30:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724135412; cv=none; b=mVoDb13UNtRmH6lSPN2H9FrMhcNXA6t7Gov7Emp0JFaGdgi/IEALQmu3MPn/r6S0Zs+DicXGSwcZVeXmYbglACi9dfOcA7nVl3axDtGY2vNc5RF8UtrH7HQieaYaxgpHbGioo/hXOmoXFOCtcTO/xWyYZwdHS84c8KTcR3IN32Q= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724135412; c=relaxed/simple; bh=R4TOefOxndRBCPUXtpdDEsXMvKoXT/g+AiM/wcdCOiI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=cngrEnGiQZfKKmRwqcwsS8nAuSglItaU6ZZNBdUrbaEgCCbV3ZjrRRAQvJma+ng5/mOR32KkznLG0Bcjoe++Htu51hvaGM+ncH88jdMEnjhFLSDIO7qfc4WwqMleKKW/BkO93FMZ40D+cJ8bG7ZbXBd2dfPW7L1nlLd01012HBc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=JoHyeatM; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=ClkIjKV+; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="JoHyeatM"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="ClkIjKV+" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1724135408; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ElxI59csI9kczE5ClB/S01RcILMnwACUfY2TZOkMQ4U=; b=JoHyeatMCnmKRPRHgthJM7/1nUTwBhU+wT8BCo/mp44hEBO5+yNjBUsGZ1pOTHnZNfXT06 lUse3PXibj0w8U96MeLLZQmjkWYaLv1AHH4a/G9eByHiiA8APVPdK4uP6Skj/F2hWRP3JR CKFH849fTBa5WkCGlB+XzKiR342Zc2xkJ0YqA9MdN0s6/rMfN5k5LzOgQh08skSgzq49PL X/pCIPEu07f4mFiMmVrlYSm2bwu0Zjtlq5tImXv0CSEgQfYKvI6n6CvopaRhiK66BPhuP1 rPx5TKtkUMithTktcwLKOaTTQEQ1Dy1sU5vRS9xXkrc4SL9Ma4jwJWfSzeCClw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1724135408; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ElxI59csI9kczE5ClB/S01RcILMnwACUfY2TZOkMQ4U=; b=ClkIjKV+8w/CdQtbj4gYDFknd1XAWfeQu9aOMAs9rgjTzac0rSj01UQA4sPBrOxpSzoI5h JBDfiLk4OmYusqDg== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby , linux-serial@vger.kernel.org Subject: [PATCH printk v8 14/35] serial: core: Acquire nbcon context in port->lock wrapper Date: Tue, 20 Aug 2024 08:35:40 +0206 Message-Id: <20240820063001.36405-15-john.ogness@linutronix.de> In-Reply-To: <20240820063001.36405-1-john.ogness@linutronix.de> References: <20240820063001.36405-1-john.ogness@linutronix.de> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Currently the port->lock wrappers uart_port_lock(), uart_port_unlock() (and their variants) only lock/unlock the spin_lock. If the port is an nbcon console that has implemented the write_atomic() callback, the wrappers must also acquire/release the console context and mark the region as unsafe. This allows general port->lock synchronization to be synchronized against the nbcon write_atomic() callback. Note that __uart_port_using_nbcon() relies on the port->lock being held while a console is added and removed from the console list (i.e. all uart nbcon drivers *must* take the port->lock in their device_lock() callbacks). Signed-off-by: John Ogness Acked-by: Greg Kroah-Hartman Reviewed-by: Petr Mladek --- include/linux/serial_core.h | 82 ++++++++++++++++++++++++++++++++++++- 1 file changed, 80 insertions(+), 2 deletions(-) diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 2cf03ff2056a..4ab65874a850 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -11,6 +11,8 @@ #include #include #include +#include +#include #include #include #include @@ -625,6 +627,60 @@ static inline void uart_port_set_cons(struct uart_port *up, struct console *con) up->cons = con; __uart_port_unlock_irqrestore(up, flags); } + +/* Only for internal port lock wrapper usage. */ +static inline bool __uart_port_using_nbcon(struct uart_port *up) +{ + lockdep_assert_held_once(&up->lock); + + if (likely(!uart_console(up))) + return false; + + /* + * @up->cons is only modified under the port lock. Therefore it is + * certain that it cannot disappear here. + * + * @up->cons->node is added/removed from the console list under the + * port lock. Therefore it is certain that the registration status + * cannot change here, thus @up->cons->flags can be read directly. + */ + if (hlist_unhashed_lockless(&up->cons->node) || + !(up->cons->flags & CON_NBCON) || + !up->cons->write_atomic) { + return false; + } + + return true; +} + +/* Only for internal port lock wrapper usage. */ +static inline bool __uart_port_nbcon_try_acquire(struct uart_port *up) +{ + if (!__uart_port_using_nbcon(up)) + return true; + + return nbcon_device_try_acquire(up->cons); +} + +/* Only for internal port lock wrapper usage. */ +static inline void __uart_port_nbcon_acquire(struct uart_port *up) +{ + if (!__uart_port_using_nbcon(up)) + return; + + while (!nbcon_device_try_acquire(up->cons)) + cpu_relax(); +} + +/* Only for internal port lock wrapper usage. */ +static inline void __uart_port_nbcon_release(struct uart_port *up) +{ + if (!__uart_port_using_nbcon(up)) + return; + + nbcon_device_release(up->cons); +} + /** * uart_port_lock - Lock the UART port * @up: Pointer to UART port structure @@ -632,6 +688,7 @@ static inline void uart_port_set_cons(struct uart_port *up, struct console *con) static inline void uart_port_lock(struct uart_port *up) { spin_lock(&up->lock); + __uart_port_nbcon_acquire(up); } /** @@ -641,6 +698,7 @@ static inline void uart_port_lock(struct uart_port *up) static inline void uart_port_lock_irq(struct uart_port *up) { spin_lock_irq(&up->lock); + __uart_port_nbcon_acquire(up); } /** @@ -651,6 +709,7 @@ static inline void uart_port_lock_irq(struct uart_port *up) static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags) { spin_lock_irqsave(&up->lock, *flags); + __uart_port_nbcon_acquire(up); } /** @@ -661,7 +720,15 @@ static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *f */ static inline bool uart_port_trylock(struct uart_port *up) { - return spin_trylock(&up->lock); + if (!spin_trylock(&up->lock)) + return false; + + if (!__uart_port_nbcon_try_acquire(up)) { + spin_unlock(&up->lock); + return false; + } + + return true; } /** @@ -673,7 +740,15 @@ static inline bool uart_port_trylock(struct uart_port *up) */ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long *flags) { - return spin_trylock_irqsave(&up->lock, *flags); + if (!spin_trylock_irqsave(&up->lock, *flags)) + return false; + + if (!__uart_port_nbcon_try_acquire(up)) { + spin_unlock_irqrestore(&up->lock, *flags); + return false; + } + + return true; } /** @@ -682,6 +757,7 @@ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long */ static inline void uart_port_unlock(struct uart_port *up) { + __uart_port_nbcon_release(up); spin_unlock(&up->lock); } @@ -691,6 +767,7 @@ static inline void uart_port_unlock(struct uart_port *up) */ static inline void uart_port_unlock_irq(struct uart_port *up) { + __uart_port_nbcon_release(up); spin_unlock_irq(&up->lock); } @@ -701,6 +778,7 @@ static inline void uart_port_unlock_irq(struct uart_port *up) */ static inline void uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags) { + __uart_port_nbcon_release(up); spin_unlock_irqrestore(&up->lock, flags); }