From patchwork Mon Jul 30 11:58:13 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anton Vorontsov X-Patchwork-Id: 1254371 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by patchwork2.kernel.org (Postfix) with ESMTP id 47D22DF24C for ; Mon, 30 Jul 2012 12:10:43 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1Svoiz-0006r9-11; Mon, 30 Jul 2012 12:05:25 +0000 Received: from mail-pb0-f49.google.com ([209.85.160.49]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1SvofT-0006Gb-1f for linux-arm-kernel@lists.infradead.org; Mon, 30 Jul 2012 12:01:47 +0000 Received: by mail-pb0-f49.google.com with SMTP id rq13so10574805pbb.36 for ; Mon, 30 Jul 2012 05:01:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references :x-gm-message-state; bh=vIkPT4AR+B8xJtWJ+Yb/N3oDCKB0J5pt5yiAzntRiXY=; b=miIogkDngLu7JJCu5/K+KyVb7NfgcRuCS5oxMuUZYxTTuXLJon3ZqFRwwjE+sZ0CN2 I+kbWvzSDhcidLRb1qqaj5y0fkTDZiMC9Qjglsv32E7Te/YXby51gZA/8xjqPeYSwanC jOFhYs+cMP6166JjYg34trDMWXINTj06gBRzg37S1igDZsZBpbxh8hMUhat7rGwGT7fB VSWTOOYoLNAltiTD3mae1GZiDy4iOtD9DaZ7WSSm9Tkq98BdxDswX4hOCKU4tkHwopZm EHBtySXdcooInOCmoPu7vOns/r5ylfH3yJC2iCx19bzzyXEwQ5UwaEYsTbAtXm8khRo1 8ttg== Received: by 10.68.223.129 with SMTP id qu1mr34205276pbc.165.1343649706714; Mon, 30 Jul 2012 05:01:46 -0700 (PDT) Received: from localhost (c-71-204-165-222.hsd1.ca.comcast.net. [71.204.165.222]) by mx.google.com with ESMTPS id nk3sm7816478pbc.27.2012.07.30.05.01.45 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 30 Jul 2012 05:01:46 -0700 (PDT) From: Anton Vorontsov To: Russell King , Jason Wessel , Greg Kroah-Hartman , Alan Cox Subject: [PATCH 04/11] tty/serial/kgdboc: Add and wire up clear_irqs callback Date: Mon, 30 Jul 2012 04:58:13 -0700 Message-Id: <1343649500-18491-4-git-send-email-anton.vorontsov@linaro.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <20120730115719.GA5742@lizard> References: <20120730115719.GA5742@lizard> X-Gm-Message-State: ALoCoQkBnQMTUxrL336m824JHgrtsGKwdnASiJsygxadeBolPSuEuJyRjbEBbq7Gv6NnjitBcX6l X-Spam-Note: CRM114 invocation failed X-Spam-Note: SpamAssassin invocation failed Cc: linaro-kernel@lists.linaro.org, patches@linaro.org, kgdb-bugreport@lists.sourceforge.net, linux-kernel@vger.kernel.org, =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , John Stultz , Colin Cross , kernel-team@android.com, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org This patch implements a new callback: clear_irqs. It is used for the cases when KDB-entry (e.g. NMI) and KDB IO (e.g. serial port) shares the same interrupt. To get the idea, let's take some real example (ARM machine): we have a serial port which interrupt is routed to an NMI, and the interrupt is used to enter KDB. Once there is some activity on the serial port, the CPU receives NMI exception, and we fall into KDB shell. So, it is our "debug console", and it is able to interrupt (and thus debug) even IRQ handlers themselves. When used that way, the interrupt never reaches serial driver's IRQ handler routine, which means that serial driver will not silence the interrupt. NMIs behaviour are quite arch-specific, and we can't assume that we can use them as ordinary IRQs, e.g. on some arches (like ARM) we can't handle data aborts, the behaviour is undefined then. So we can't just handle execution to serial driver's IRQ handler from the NMI context once we're done with KDB (plus this would defeat the debugger's purpose: we want the NMI handler be as simple as possible, so it will have less chances to hang). So, given that have to deal with it somehow, we have two options: 1. Implement something that clears the interrupt; 2. Implement a whole new concept of grabbing tty for exclusive KDB use, plus implement mask/unmask callbacks, i.e.: - Since consoles might use ttys w/o opending them, we would have to make kdb respect CON_ENABLED flag (maybe a good idea to do it anyway); - Add 'bool exclusive' argument to tty_find_polling_driver(), if set to 1, the function will refuse to return an already tty; and will use the flag in tty_reopen() to not allow multiple users (there are already checks for pty masters, which are "open once" ttys); - Once we got the tty exclusively, we would need to call some new uart->mask_all_but_rx_interrupts call before we want to use the port for NMI/KDB, and unmask_all_but_rx_interrupts after we're done with it. The second option is obviously more complex, needlessly so, and less generic. So I went with the first one: we just consume all the interrupts. The tty becomes silently unusable for the rest of the world when we use it with KDB; but once we reroute the serial IRQ source back from NMI to an ordinary IRQ (in KDB this can be done with 'disable_nmi' command), it will behave as normal. p.s. Since the callback is so far used only by polling user, we place it under the appropriate #ifdef. Signed-off-by: Anton Vorontsov --- drivers/tty/serial/kgdboc.c | 9 +++++++++ drivers/tty/serial/serial_core.c | 15 +++++++++++++++ include/linux/kgdb.h | 1 + include/linux/serial_core.h | 1 + include/linux/tty_driver.h | 1 + 5 files changed, 27 insertions(+) diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index 2b42a01..178e62c 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -227,6 +227,14 @@ static int kgdboc_get_char(void) kgdb_tty_line); } +static void kgdboc_clear_irqs(void) +{ + if (!kgdb_tty_driver) + return; + if (kgdb_tty_driver->ops->clear_irqs) + kgdb_tty_driver->ops->clear_irqs(kgdb_tty_driver, kgdb_tty_line); +} + static void kgdboc_put_char(u8 chr) { if (!kgdb_tty_driver) @@ -298,6 +306,7 @@ static struct kgdb_io kgdboc_io_ops = { .name = "kgdboc", .read_char = kgdboc_get_char, .write_char = kgdboc_put_char, + .clear_irqs = kgdboc_clear_irqs, .pre_exception = kgdboc_pre_exp_handler, .post_exception = kgdboc_post_exp_handler, }; diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 246b823..89c4093 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -2154,6 +2154,20 @@ static void uart_poll_put_char(struct tty_driver *driver, int line, char ch) port = state->uart_port; port->ops->poll_put_char(port, ch); } + +static void uart_clear_irqs(struct tty_driver *driver, int line) +{ + struct uart_driver *drv = driver->driver_state; + struct uart_state *state = drv->state + line; + struct uart_port *port; + + if (!state || !state->uart_port) + return; + + port = state->uart_port; + if (port->ops->clear_irqs) + port->ops->clear_irqs(port); +} #endif static const struct tty_operations uart_ops = { @@ -2186,6 +2200,7 @@ static const struct tty_operations uart_ops = { .poll_init = uart_poll_init, .poll_get_char = uart_poll_get_char, .poll_put_char = uart_poll_put_char, + .clear_irqs = uart_clear_irqs, #endif }; diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h index e0c0a2e..f695b26 100644 --- a/include/linux/kgdb.h +++ b/include/linux/kgdb.h @@ -285,6 +285,7 @@ struct kgdb_io { const char *name; int (*read_char) (void); void (*write_char) (u8); + void (*clear_irqs) (void); void (*flush) (void); int (*init) (void); void (*pre_exception) (void); diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 65db992..081d300 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -275,6 +275,7 @@ struct uart_ops { #ifdef CONFIG_CONSOLE_POLL void (*poll_put_char)(struct uart_port *, unsigned char); int (*poll_get_char)(struct uart_port *); + void (*clear_irqs)(struct uart_port *); #endif }; diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h index 6e6dbb7..94b14cd 100644 --- a/include/linux/tty_driver.h +++ b/include/linux/tty_driver.h @@ -287,6 +287,7 @@ struct tty_operations { int (*poll_init)(struct tty_driver *driver, int line, char *options); int (*poll_get_char)(struct tty_driver *driver, int line); void (*poll_put_char)(struct tty_driver *driver, int line, char ch); + void (*clear_irqs)(struct tty_driver *driver, int line); #endif const struct file_operations *proc_fops; };