From patchwork Thu May 25 09:31:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Ogness X-Patchwork-Id: 686350 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 100E1C7EE2E for ; Thu, 25 May 2023 09:35:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240699AbjEYJfL (ORCPT ); Thu, 25 May 2023 05:35:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240660AbjEYJem (ORCPT ); Thu, 25 May 2023 05:34:42 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 529FEE42; Thu, 25 May 2023 02:34:37 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1685007271; 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=vZVepLjGQmA8Sd7Dsoz91hGyNnRRVtsxo9tL/VycGyM=; b=uZ3fJDvn3TkdggxynrSMSfRfldyWS4BjQknTKnFLPsovz8j7ATjj9wKY0YrNVgjmstnPDp RpaZS25BsNwZGpaoJ/p7EJJ0uIbBlS2FUZb7JOxDaj01/dymaraJMQq3HMBNo8AdoDtjj9 zicPN9Y+n59Eio5tvFDuMNg3FqCmngFYk44jhQfhJmmgYQqabA/sWVdNy5FxqS89PuRfOd aIlGwXIVvB3HqG5QjnSzYqSFoy17PnFrpG0S42MoYhVVriluyO/v7qDu49txvu1bQtu0UR T/hMyr5UmoePZahxw43d/YnRICYxjiOuqkO5KdkecSSs27EigiIE7kgVE4e+xA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1685007271; 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=vZVepLjGQmA8Sd7Dsoz91hGyNnRRVtsxo9tL/VycGyM=; b=sSWawuGzshyC+A1UZwduoT3u0VBy5TcXDOddQy8qoXvVAcuzGJyKZcT9rD6R+qnYz6FWGe gQLD6b6k+lHbNkAw== To: Greg Kroah-Hartman Cc: Petr Mladek , Thomas Gleixner , linux-kernel@vger.kernel.org, Jiri Slaby , Joel Stanley , Andrew Jeffery , Matthias Brugger , AngeloGioacchino Del Regno , =?utf-8?q?Ilpo_J=C3=A4rvinen?= , Andy Shevchenko , Tony Lindgren , Lukas Wunner , Matthias Schiffer , =?utf-8?q?Uwe_Kleine?= =?utf-8?q?-K=C3=B6nig?= , linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-mediatek@lists.infradead.org Subject: [PATCH tty v1 8/8] serial: 8250: synchronize and annotate UART_IER access Date: Thu, 25 May 2023 11:37:59 +0206 Message-Id: <20230525093159.223817-9-john.ogness@linutronix.de> In-Reply-To: <20230525093159.223817-1-john.ogness@linutronix.de> References: <20230525093159.223817-1-john.ogness@linutronix.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org The UART_IER register is modified twice by each console write (serial8250_console_write()) under the port lock. Any driver code that accesses UART_IER must do so with the port locked in order to ensure consistent values, even when for read accesses. Add locking, lockdep notation, and/or comments everywhere UART_IER is accessed. The added locking is not fixing a real problem because it occurs where the console is not active. However, adding the locking to these non-critical paths greatly simplifies UART_IER access tracking by establishing a general policy that all UART_IER access is performed with the port locked. Signed-off-by: John Ogness --- drivers/tty/serial/8250/8250.h | 6 +++ drivers/tty/serial/8250/8250_aspeed_vuart.c | 3 ++ drivers/tty/serial/8250/8250_mtk.c | 9 ++++ drivers/tty/serial/8250/8250_omap.c | 14 ++++++ drivers/tty/serial/8250/8250_port.c | 53 +++++++++++++++++++++ 5 files changed, 85 insertions(+) diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h index 5418708f4631..471c6bc5f78f 100644 --- a/drivers/tty/serial/8250/8250.h +++ b/drivers/tty/serial/8250/8250.h @@ -179,6 +179,9 @@ static inline void serial_dl_write(struct uart_8250_port *up, u32 value) static inline bool serial8250_set_THRI(struct uart_8250_port *up) { + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + if (up->ier & UART_IER_THRI) return false; up->ier |= UART_IER_THRI; @@ -188,6 +191,9 @@ static inline bool serial8250_set_THRI(struct uart_8250_port *up) static inline bool serial8250_clear_THRI(struct uart_8250_port *up) { + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + if (!(up->ier & UART_IER_THRI)) return false; up->ier &= ~UART_IER_THRI; diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c index 9d2a7856784f..4a9e71b2dbbc 100644 --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c @@ -275,6 +275,9 @@ static void __aspeed_vuart_set_throttle(struct uart_8250_port *up, { unsigned char irqs = UART_IER_RLSI | UART_IER_RDI; + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + up->ier &= ~irqs; if (!throttle) up->ier |= irqs; diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c index fb1d5ec0940e..aa8e98164d68 100644 --- a/drivers/tty/serial/8250/8250_mtk.c +++ b/drivers/tty/serial/8250/8250_mtk.c @@ -222,11 +222,17 @@ static void mtk8250_shutdown(struct uart_port *port) static void mtk8250_disable_intrs(struct uart_8250_port *up, int mask) { + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + serial_out(up, UART_IER, serial_in(up, UART_IER) & (~mask)); } static void mtk8250_enable_intrs(struct uart_8250_port *up, int mask) { + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + serial_out(up, UART_IER, serial_in(up, UART_IER) | mask); } @@ -235,6 +241,9 @@ static void mtk8250_set_flow_ctrl(struct uart_8250_port *up, int mode) struct uart_port *port = &up->port; int lcr = serial_in(up, UART_LCR); + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&port->lock); + serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B); serial_out(up, MTK_UART_EFR, UART_EFR_ECB); serial_out(up, UART_LCR, lcr); diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 3225c95fde1d..0498b9b0e4e9 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -533,6 +533,10 @@ static void omap_8250_pm(struct uart_port *port, unsigned int state, u8 efr; pm_runtime_get_sync(port->dev); + + /* Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); + serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B); efr = serial_in(up, UART_EFR); serial_out(up, UART_EFR, efr | UART_EFR_ECB); @@ -543,6 +547,8 @@ static void omap_8250_pm(struct uart_port *port, unsigned int state, serial_out(up, UART_EFR, efr); serial_out(up, UART_LCR, 0); + spin_unlock_irq(&port->lock); + pm_runtime_mark_last_busy(port->dev); pm_runtime_put_autosuspend(port->dev); } @@ -760,8 +766,11 @@ static void omap_8250_shutdown(struct uart_port *port) if (priv->habit & UART_HAS_EFR2) serial_out(up, UART_OMAP_EFR2, 0x0); + /* Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); up->ier = 0; serial_out(up, UART_IER, 0); + spin_unlock_irq(&port->lock); disable_irq_nosync(up->port.irq); dev_pm_clear_wake_irq(port->dev); @@ -803,6 +812,7 @@ static void omap_8250_unthrottle(struct uart_port *port) pm_runtime_get_sync(port->dev); + /* Synchronize UART_IER access against the console. */ spin_lock_irqsave(&port->lock, flags); priv->throttled = false; if (up->dma) @@ -953,6 +963,7 @@ static void __dma_rx_complete(void *param) struct dma_tx_state state; unsigned long flags; + /* Synchronize UART_IER access against the console. */ spin_lock_irqsave(&p->port.lock, flags); /* @@ -1227,6 +1238,9 @@ static u16 omap_8250_handle_rx_dma(struct uart_8250_port *up, u8 iir, u16 status static void am654_8250_handle_rx_dma(struct uart_8250_port *up, u8 iir, u16 status) { + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + /* * Queue a new transfer if FIFO has data. */ diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index b3971302d8e5..4b7bbd8b3305 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -539,6 +539,9 @@ EXPORT_SYMBOL_GPL(serial8250_rpm_put); */ static int serial8250_em485_init(struct uart_8250_port *p) { + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&p->port.lock); + if (p->em485) goto deassert_rts; @@ -676,6 +679,8 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) serial8250_rpm_get(p); if (p->capabilities & UART_CAP_SLEEP) { + /* Synchronize UART_IER access against the console. */ + spin_lock_irq(&p->port.lock); if (p->capabilities & UART_CAP_EFR) { lcr = serial_in(p, UART_LCR); efr = serial_in(p, UART_EFR); @@ -689,6 +694,7 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) serial_out(p, UART_EFR, efr); serial_out(p, UART_LCR, lcr); } + spin_unlock_irq(&p->port.lock); } serial8250_rpm_put(p); @@ -696,6 +702,9 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) static void serial8250_clear_IER(struct uart_8250_port *up) { + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + if (up->capabilities & UART_CAP_UUE) serial_out(up, UART_IER, UART_IER_UUE); else @@ -968,6 +977,9 @@ static void autoconfig_16550a(struct uart_8250_port *up) unsigned char status1, status2; unsigned int iersave; + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + up->port.type = PORT_16550A; up->capabilities |= UART_CAP_FIFO; @@ -1151,6 +1163,8 @@ static void autoconfig(struct uart_8250_port *up) /* * We really do need global IRQs disabled here - we're going to * be frobbing the chips IRQ enable register to see if it exists. + * + * Synchronize UART_IER access against the console. */ spin_lock_irqsave(&port->lock, flags); @@ -1323,7 +1337,10 @@ static void autoconfig_irq(struct uart_8250_port *up) /* forget possible initially masked and pending IRQ */ probe_irq_off(probe_irq_on()); save_mcr = serial8250_in_MCR(up); + /* Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); save_ier = serial_in(up, UART_IER); + spin_unlock_irq(&port->lock); serial8250_out_MCR(up, UART_MCR_OUT1 | UART_MCR_OUT2); irqs = probe_irq_on(); @@ -1335,7 +1352,10 @@ static void autoconfig_irq(struct uart_8250_port *up) serial8250_out_MCR(up, UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2); } + /* Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); serial_out(up, UART_IER, UART_IER_ALL_INTR); + spin_unlock_irq(&port->lock); serial_in(up, UART_LSR); serial_in(up, UART_RX); serial_in(up, UART_IIR); @@ -1345,7 +1365,10 @@ static void autoconfig_irq(struct uart_8250_port *up) irq = probe_irq_off(irqs); serial8250_out_MCR(up, save_mcr); + /* Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); serial_out(up, UART_IER, save_ier); + spin_unlock_irq(&port->lock); if (port->flags & UPF_FOURPORT) outb_p(save_ICP, ICP); @@ -1360,6 +1383,9 @@ static void serial8250_stop_rx(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&port->lock); + serial8250_rpm_get(up); up->ier &= ~(UART_IER_RLSI | UART_IER_RDI); @@ -1379,6 +1405,9 @@ void serial8250_em485_stop_tx(struct uart_8250_port *p) { unsigned char mcr = serial8250_in_MCR(p); + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&p->port.lock); + if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) mcr |= UART_MCR_RTS; else @@ -1428,6 +1457,9 @@ static void __stop_tx_rs485(struct uart_8250_port *p, u64 stop_delay) { struct uart_8250_em485 *em485 = p->em485; + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&p->port.lock); + stop_delay += (u64)p->port.rs485.delay_rts_after_send * NSEC_PER_MSEC; /* @@ -1607,6 +1639,9 @@ static void serial8250_start_tx(struct uart_port *port) struct uart_8250_port *up = up_to_u8250p(port); struct uart_8250_em485 *em485 = up->em485; + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&port->lock); + if (!port->x_char && uart_circ_empty(&port->state->xmit)) return; @@ -1634,6 +1669,9 @@ static void serial8250_disable_ms(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&port->lock); + /* no MSR capabilities */ if (up->bugs & UART_BUG_NOMSR) return; @@ -1648,6 +1686,9 @@ static void serial8250_enable_ms(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&port->lock); + /* no MSR capabilities */ if (up->bugs & UART_BUG_NOMSR) return; @@ -2104,6 +2145,14 @@ static void serial8250_put_poll_char(struct uart_port *port, unsigned int ier; struct uart_8250_port *up = up_to_u8250p(port); + /* + * Normally the port is locked to synchronize UART_IER access + * against the console. However, this function is only used by + * KDB/KGDB, where it may not be possible to acquire the port + * lock because all other CPUs are quiesced. The quiescence + * should allow safe lockless usage here. + */ + serial8250_rpm_get(up); /* * First save the IER then disable the interrupts @@ -2439,6 +2488,8 @@ void serial8250_do_shutdown(struct uart_port *port) serial8250_rpm_get(up); /* * Disable interrupts from this port + * + * Synchronize UART_IER access against the console. */ spin_lock_irqsave(&port->lock, flags); up->ier = 0; @@ -2738,6 +2789,8 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, /* * Ok, we're now changing the port state. Do it with * interrupts disabled. + * + * Synchronize UART_IER access against the console. */ serial8250_rpm_get(up); spin_lock_irqsave(&port->lock, flags);