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[86.9.19.6]) by smtp.gmail.com with ESMTPSA id j18sm18502577wrn.59.2020.06.22.09.03.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jun 2020 09:03:02 -0700 (PDT) Date: Mon, 22 Jun 2020 17:03:00 +0100 From: Daniel Thompson To: Sumit Garg Cc: kgdb-bugreport@lists.sourceforge.net, linux-serial@vger.kernel.org, gregkh@linuxfoundation.org, jason.wessel@windriver.com, dianders@chromium.org, jslaby@suse.com, linux@armlinux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/7] kgdb: Add request_nmi() to the io ops table for kgdboc Message-ID: <20200622160300.avgfhnfkpqzqqtsr@holly.lan> References: <1592835984-28613-1-git-send-email-sumit.garg@linaro.org> <1592835984-28613-4-git-send-email-sumit.garg@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1592835984-28613-4-git-send-email-sumit.garg@linaro.org> Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Mon, Jun 22, 2020 at 07:56:20PM +0530, Sumit Garg wrote: > From: Daniel Thompson > > Add request_nmi() callback to install a non-maskable interrupt handler > corresponding to IRQ retrieved from polling interface. If NMI handler > installation fails due to missing support from underlying irqchip driver > then fallback to install it as normal interrupt handler. > > Signed-off-by: Daniel Thompson > Co-developed-by: Sumit Garg > Signed-off-by: Sumit Garg > --- > drivers/tty/serial/kgdboc.c | 35 +++++++++++++++++++++++++++++++++++ > include/linux/kgdb.h | 7 +++++++ > 2 files changed, 42 insertions(+) > > diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c > index 84ffede..263afae 100644 > --- a/drivers/tty/serial/kgdboc.c > +++ b/drivers/tty/serial/kgdboc.c > @@ -19,6 +19,9 @@ > #include > #include > #include > +#include > +#include > +#include > #include > #include > #include > @@ -390,12 +393,44 @@ static void kgdboc_post_exp_handler(void) > kgdboc_restore_input(); > } > > +static int kgdb_tty_irq; > + > +static int kgdboc_request_nmi(irq_handler_t fn, void *dev_id) > +{ > + int irq, res; > + > + /* Better to avoid double allocation in the tty driver! */ > + if (kgdb_tty_irq) > + return 0; > + > + if (!kgdb_tty_driver->ops->poll_get_irq) > + return -ENODEV; > + > + irq = > + kgdb_tty_driver->ops->poll_get_irq(kgdb_tty_driver, kgdb_tty_line); > + if (irq <= 0) > + return irq ? irq : -ENODEV; > + > + irq_set_status_flags(irq, IRQ_NOAUTOEN); > + res = request_nmi(irq, fn, IRQF_PERCPU, "kgdboc", dev_id); Why do we need IRQF_PERCPU here. A UART interrupt is not normally per-cpu? > + if (res) { > + res = request_irq(irq, fn, IRQF_SHARED, "kgdboc", dev_id); IRQF_SHARED? Currrently there is nothing that prevents concurrent activation of ttyNMI0 and the underlying serial driver. Using IRQF_SHARED means it becomes possible for both drivers to try to service the same interrupt. That risks some rather "interesting" problems. Daniel. > + WARN_ON(res); > + } > + > + enable_irq(irq); > + > + kgdb_tty_irq = irq; > + return 0; > +} > + > static struct kgdb_io kgdboc_io_ops = { > .name = "kgdboc", > .read_char = kgdboc_get_char, > .write_char = kgdboc_put_char, > .pre_exception = kgdboc_pre_exp_handler, > .post_exception = kgdboc_post_exp_handler, > + .request_nmi = kgdboc_request_nmi, > }; > > #if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) > diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h > index 529116b..b32b044 100644 > --- a/include/linux/kgdb.h > +++ b/include/linux/kgdb.h > @@ -16,6 +16,7 @@ > #include > #include > #include > +#include > #ifdef CONFIG_HAVE_ARCH_KGDB > #include > #endif > @@ -276,6 +277,10 @@ struct kgdb_arch { > * the I/O driver. > * @post_exception: Pointer to a function that will do any cleanup work > * for the I/O driver. > + * @request_nmi: Pointer to a function that can install an non-maskable > + * interrupt handler that will be called when a character is pending and that > + * can be cleared by calling @read_char until it returns NO_POLL_CHAR. If NMI > + * installation fails then fallback to install normal interrupt handler. > * @cons: valid if the I/O device is a console; else NULL. > */ > struct kgdb_io { > @@ -287,6 +292,8 @@ struct kgdb_io { > void (*deinit) (void); > void (*pre_exception) (void); > void (*post_exception) (void); > + int (*request_nmi)(irq_handler_t nmi_handler, > + void *dev_id); > struct console *cons; > }; > > -- > 2.7.4 >