From patchwork Mon Aug 20 14:47:24 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anton Vorontsov X-Patchwork-Id: 10809 Return-Path: X-Original-To: patchwork@peony.canonical.com Delivered-To: patchwork@peony.canonical.com Received: from fiordland.canonical.com (fiordland.canonical.com [91.189.94.145]) by peony.canonical.com (Postfix) with ESMTP id 8778323E56 for ; Mon, 20 Aug 2012 14:50:12 +0000 (UTC) Received: from mail-iy0-f180.google.com (mail-iy0-f180.google.com [209.85.210.180]) by fiordland.canonical.com (Postfix) with ESMTP id 48A23A18B4E for ; Mon, 20 Aug 2012 14:50:06 +0000 (UTC) Received: by mail-iy0-f180.google.com with SMTP id j38so2715925iad.11 for ; Mon, 20 Aug 2012 07:50:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-forwarded-to:x-forwarded-for:delivered-to:received-spf:from:to:cc :subject:date:message-id:x-mailer:in-reply-to:references :x-gm-message-state; bh=uPm97Kb8wsYKB+ejK2cuwYbWGfQtLIUHyhWuFfz0Pt8=; b=nd+I1vPIDx9UBRd6HIjuGjDYTFSu0Qb/vreRGcjVpITnxkVH/CYbTn2rOV5qO7mozD KYYQTF2UdIy2UrMENSREbmNYhU6fkNqFKBqjFgwXJ5hGXW8wq1+lCt9a+2n3mTPldcTc U3XZdYqjkrEg/m9KrwMbPBt47nmCL6rmdW8YinK19MPN6onlnex6yF/R1WtwQV4WjL5w 2jeEPieFe9DlEJYKoqB0UX7JCi+STaqwrdDaO5IhwcyuYS9g8WsXRwkQUlBB/DL8Vf7i enJsTHBGGhKcOz6RrIOXHQPkj4UdHnT20u8MXnzX4qxlvFPtQlxgM0sslv2sHOQvMWc1 u6hA== Received: by 10.42.84.69 with SMTP id k5mr11298717icl.5.1345474211836; Mon, 20 Aug 2012 07:50:11 -0700 (PDT) X-Forwarded-To: linaro-patchwork@canonical.com X-Forwarded-For: patch@linaro.org linaro-patchwork@canonical.com Delivered-To: patches@linaro.org Received: by 10.50.184.232 with SMTP id ex8csp87709igc; Mon, 20 Aug 2012 07:50:11 -0700 (PDT) Received: by 10.68.239.164 with SMTP id vt4mr35340528pbc.118.1345474211186; Mon, 20 Aug 2012 07:50:11 -0700 (PDT) Received: from mail-pb0-f50.google.com (mail-pb0-f50.google.com [209.85.160.50]) by mx.google.com with ESMTPS id kn7si27031018pbc.26.2012.08.20.07.50.11 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 20 Aug 2012 07:50:11 -0700 (PDT) Received-SPF: neutral (google.com: 209.85.160.50 is neither permitted nor denied by best guess record for domain of anton.vorontsov@linaro.org) client-ip=209.85.160.50; Authentication-Results: mx.google.com; spf=neutral (google.com: 209.85.160.50 is neither permitted nor denied by best guess record for domain of anton.vorontsov@linaro.org) smtp.mail=anton.vorontsov@linaro.org Received: by mail-pb0-f50.google.com with SMTP id md12so7851924pbc.37 for ; Mon, 20 Aug 2012 07:50:11 -0700 (PDT) Received: by 10.66.75.228 with SMTP id f4mr30146893paw.52.1345474210845; Mon, 20 Aug 2012 07:50:10 -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 os1sm11237088pbc.31.2012.08.20.07.50.09 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 20 Aug 2012 07:50:10 -0700 (PDT) From: Anton Vorontsov To: Russell King , Jason Wessel , Greg Kroah-Hartman , Alan Cox Cc: =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Colin Cross , John Stultz , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linaro-kernel@lists.linaro.org, patches@linaro.org, kernel-team@android.com, kgdb-bugreport@lists.sourceforge.net Subject: [PATCH 06/12] tty/serial/kgdboc: Add and wire up clear_irqs callback Date: Mon, 20 Aug 2012 07:47:24 -0700 Message-Id: <1345474050-8339-6-git-send-email-anton.vorontsov@linaro.org> X-Mailer: git-send-email 1.7.11.5 In-Reply-To: <20120820144449.GA32560@lizard> References: <20120820144449.GA32560@lizard> X-Gm-Message-State: ALoCoQk1dPZpY6+2y/tBGoU/6St1qP9M1BBoKLZD0bsXb2F0jlvio8J7n2UuzQfwxsWTz9jXdDNQ 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 | 10 ++++++++++ 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, 28 insertions(+) diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index 2b42a01..0aa08c8 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -227,6 +227,15 @@ 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 +307,7 @@ 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 cba8443..908d108 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -2169,6 +2169,20 @@ 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 = { @@ -2201,6 +2215,7 @@ 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 3b111a6..1fd1cf0 100644 --- a/include/linux/kgdb.h +++ b/include/linux/kgdb.h @@ -295,6 +295,7 @@ 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 3642710..114b3f3 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -277,6 +277,7 @@ struct uart_ops { int (*poll_init)(struct uart_port *); 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; };