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Tue, 07 Jul 2020 04:47:08 -0700 (PDT) Subject: Re: [PATCH v3] softdog: Add options 'soft_reboot_cmd' and 'soft_active_on_boot' To: Woody Lin Cc: Wim Van Sebroeck , linux-watchdog@vger.kernel.org References: <20200701110339.2833449-1-woodylin@google.com> <20200707040356.GA213018@roeck-us.net> From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= Message-ID: <8e16b12c-1097-dea7-32d7-f3381568407a@roeck-us.net> Date: Tue, 7 Jul 2020 04:47:07 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On 7/7/20 1:46 AM, Woody Lin wrote: > On Tue, Jul 7, 2020 at 12:04 PM Guenter Roeck wrote: >> >> On Wed, Jul 01, 2020 at 07:03:40PM +0800, Woody Lin wrote: >>> Add module parameters 'soft_reboot_cmd' and 'soft_active_on_boot' for >>> customizing softdog configuration; config reboot command by assigning >>> soft_reboot_cmd, and set soft_active_on_boot to start up softdog >>> timer at module initialization stage. >>> >>> Signed-off-by: Woody Lin >>> --- >>> drivers/watchdog/softdog.c | 56 ++++++++++++++++++++++++++++++++++++++ >>> 1 file changed, 56 insertions(+) >>> >>> diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c >>> index 3e4885c1545e..8c8d214b6aa7 100644 >>> --- a/drivers/watchdog/softdog.c >>> +++ b/drivers/watchdog/softdog.c >>> @@ -20,11 +20,13 @@ >>> #include >>> #include >>> #include >>> +#include >>> #include >>> #include >>> #include >>> #include >>> #include >>> +#include >>> >>> #define TIMER_MARGIN 60 /* Default is 60 seconds */ >>> static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */ >>> @@ -49,11 +51,33 @@ module_param(soft_panic, int, 0); >>> MODULE_PARM_DESC(soft_panic, >>> "Softdog action, set to 1 to panic, 0 to reboot (default=0)"); >>> >>> +static char *soft_reboot_cmd; >>> +module_param(soft_reboot_cmd, charp, 0000); >>> +MODULE_PARM_DESC(soft_reboot_cmd, >>> + "Set reboot command. Emergency reboot takes place if unset"); >>> + >>> +static bool soft_active_on_boot; >>> +module_param(soft_active_on_boot, bool, 0000); >>> +MODULE_PARM_DESC(soft_active_on_boot, >>> + "Set to true to active Softdog on boot (default=false)"); >>> + >>> static struct hrtimer softdog_ticktock; >>> static struct hrtimer softdog_preticktock; >>> >>> +static int reboot_kthread_fn(void *data) >>> +{ >>> + kernel_restart(soft_reboot_cmd); >>> + return -EPERM; /* Should not reach here */ >>> +} >>> + >>> +static void reboot_work_fn(struct work_struct *unused) >>> +{ >>> + kthread_run(reboot_kthread_fn, NULL, "softdog_reboot"); >>> +} >>> + >>> static enum hrtimer_restart softdog_fire(struct hrtimer *timer) >>> { >>> + static bool soft_reboot_fired; >> >> Per coding style there should be an empty line here. > > Ack. > >> >>> module_put(THIS_MODULE); >>> if (soft_noboot) { >>> pr_crit("Triggered - Reboot ignored\n"); >>> @@ -62,6 +86,33 @@ static enum hrtimer_restart softdog_fire(struct hrtimer *timer) >>> panic("Software Watchdog Timer expired"); >>> } else { >>> pr_crit("Initiating system reboot\n"); >>> + if (!soft_reboot_fired && soft_reboot_cmd != NULL) { >>> + static DECLARE_WORK(reboot_work, reboot_work_fn); >>> + /* >>> + * The 'kernel_restart' is a 'might-sleep' operation. >>> + * Also, executing it in system-wide workqueues blocks >>> + * any driver from using the same workqueue in its >>> + * shutdown callback function. Thus, we should execute >>> + * the 'kernel_restart' in a standalone kernel thread. >>> + * But since starting a kernel thread is also a >>> + * 'might-sleep' operation, so the 'reboot_work' is >>> + * required as a launcher of the kernel thread. >>> + * >>> + * After request the reboot, restart the timer to >>> + * schedule an 'emergency_restart' reboot after >>> + * 'TIMER_MARGIN' seconds. It's because if the softdog >>> + * hangs, it might be because of scheduling issues. And >>> + * if that is the case, both 'schedule_work' and >>> + * 'kernel_restart' may possibly be malfunctional at the >>> + * same time. >>> + */ >>> + soft_reboot_fired = true; >>> + schedule_work(&reboot_work); >>> + hrtimer_add_expires_ns(timer, >>> + (u64)TIMER_MARGIN * NSEC_PER_SEC); >>> + >>> + return HRTIMER_RESTART; >>> + } >>> emergency_restart(); >>> pr_crit("Reboot didn't ?????\n"); >>> } >>> @@ -145,12 +196,17 @@ static int __init softdog_init(void) >>> softdog_preticktock.function = softdog_pretimeout; >>> } >>> >>> + if (soft_active_on_boot) >>> + softdog_ping(&softdog_dev); >>> + >>> ret = watchdog_register_device(&softdog_dev); >>> if (ret) >>> return ret; >>> >>> pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n", >>> soft_noboot, softdog_dev.timeout, soft_panic, nowayout); >>> + pr_info(" soft_reboot_cmd=%s soft_active_on_boot=%d\n", >>> + soft_reboot_cmd, soft_active_on_boot); >> >> soft_reboot_cmd can be NULL, which makes the output a bit awkward. > > Then how about change it to something like this: > "soft_reboot_cmd=%s", soft_reboot_cmd ?: " (emergency reboot)" > Then we will see "soft_reboot_cmd= (emergency reboot)" when it's NULL. I'd rather see something like "". "" looks like an error. Also, it isn't correct to assume emergency reboot; that is only correct if neither soft_noboot nor soft_panic is set. Thanks, Guenter