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Tue, 09 Jun 2020 10:18:31 -0700 (PDT) Subject: Re: [PATCH] softdog: Add options 'soft_reboot_target' and 'soft_active_on_boot' To: Woody Lin , Wim Van Sebroeck Cc: linux-watchdog@vger.kernel.org References: <20200603103923.116113-1-woodylin@google.com> 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: <938e6176-aa35-8613-231e-31fb37fd09b1@roeck-us.net> Date: Tue, 9 Jun 2020 10:18:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200603103923.116113-1-woodylin@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On 6/3/20 3:39 AM, Woody Lin wrote: > Add module parameters 'soft_reboot_target' and 'soft_active_on_boot' for > customizing softdog configuration; config reboot target by assigning > soft_reboot_target, and set soft_active_on_boot to start up softdog > timer at module initialization stage. > > Signed-off-by: Woody Lin > --- > drivers/watchdog/softdog.c | 38 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c > index 3e4885c1545e..f5027acddbbb 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 */ > @@ -49,9 +51,32 @@ 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_target; > +module_param(soft_reboot_target, charp, 0000); > +MODULE_PARM_DESC(soft_reboot_target, > + "Softdog action, set reboot target (default=emergency)"); > + > +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_target); > + emergency_restart(); /* Should not reach here */ > + return -EPERM; /* Should not reach here */ > +} > + > +static void reboot_work_fn(struct work_struct *unused) > +{ > + if (IS_ERR(kthread_run(reboot_kthread_fn, NULL, "softdog_reboot"))) > + emergency_restart(); > +} > + > static enum hrtimer_restart softdog_fire(struct hrtimer *timer) > { > module_put(THIS_MODULE); > @@ -62,6 +87,12 @@ static enum hrtimer_restart softdog_fire(struct hrtimer *timer) > panic("Software Watchdog Timer expired"); > } else { > pr_crit("Initiating system reboot\n"); > + if (soft_reboot_target != NULL) { > + static DECLARE_WORK(reboot_work, reboot_work_fn); > + > + schedule_work(&reboot_work); > + return HRTIMER_NORESTART; > + } So this adds a double indirection: It first schedules a worker, then the worker creates a kernel thread, which finally calls kernel_restart(). If the softdog hangs, it may well be because of scheduling issues. If so, both the worker and the kernel thread may never execute, and the system would not reboot even though the softdog did fire. Is this double indirection really necessary ? Thanks, Guenter > emergency_restart(); > pr_crit("Reboot didn't ?????\n"); > } > @@ -145,12 +176,19 @@ static int __init softdog_init(void) > softdog_preticktock.function = softdog_pretimeout; > } > > + if (soft_active_on_boot) { > + set_bit(WDOG_HW_RUNNING, &softdog_dev.status); > + set_bit(WDOG_ACTIVE, &softdog_dev.status); > + } > + > 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_target=%s soft_active_on_boot=%d\n", > + soft_reboot_target, soft_active_on_boot); > > return 0; > } >