Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753245AbdDRENc (ORCPT ); Tue, 18 Apr 2017 00:13:32 -0400 Received: from lelnx194.ext.ti.com ([198.47.27.80]:48315 "EHLO lelnx194.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750723AbdDREN3 (ORCPT ); Tue, 18 Apr 2017 00:13:29 -0400 Subject: Re: [PATCH v5 2/2] thermal: core: Add a back up thermal shutdown mechanism To: Eduardo Valentin References: <1492225709-30932-1-git-send-email-j-keerthy@ti.com> <1492225709-30932-2-git-send-email-j-keerthy@ti.com> <20170417171616.GA9889@localhost.localdomain> CC: , , , , , From: Keerthy Message-ID: Date: Tue, 18 Apr 2017 09:43:23 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170417171616.GA9889@localhost.localdomain> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7507 Lines: 190 On Monday 17 April 2017 10:46 PM, Eduardo Valentin wrote: > On Sat, Apr 15, 2017 at 08:38:29AM +0530, Keerthy wrote: >> orderly_poweroff is triggered when a graceful shutdown >> of system is desired. This may be used in many critical states of the >> kernel such as when subsystems detects conditions such as critical >> temperature conditions. However, in certain conditions in system >> boot up sequences like those in the middle of driver probes being >> initiated, userspace will be unable to power off the system in a clean >> manner and leaves the system in a critical state. In cases like these, >> the /sbin/poweroff will return success (having forked off to attempt >> powering off the system. However, the system overall will fail to >> completely poweroff (since other modules will be probed) and the system >> is still functional with no userspace (since that would have shut itself >> off). >> >> However, there is no clean way of detecting such failure of userspace >> powering off the system. In such scenarios, it is necessary for a backup >> workqueue to be able to force a shutdown of the system when orderly >> shutdown is not successful after a configurable time period. >> >> Reported-by: Nishanth Menon >> Signed-off-by: Keerthy >> --- >> >> Changes in v5: >> >> * Mandated delay for thermal emergency poweroff to be a non-zero value. >> >> Changes in v4: >> >> * Updated documentation >> * changed emergency_poweroff_func to thermal_emergency_poweroff_func >> >> Changes in v3: >> >> * Removed unnecessary mutex init. >> * Added WARN messages instead of a simple warning message. >> * Added Documentation. >> >> Documentation/thermal/sysfs-api.txt | 21 +++++++++++++++ >> drivers/thermal/Kconfig | 15 +++++++++++ >> drivers/thermal/thermal_core.c | 53 +++++++++++++++++++++++++++++++++++++ >> 3 files changed, 89 insertions(+) >> >> diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt >> index ef473dc..98dc04f 100644 >> --- a/Documentation/thermal/sysfs-api.txt >> +++ b/Documentation/thermal/sysfs-api.txt >> @@ -582,3 +582,24 @@ platform data is provided, this uses the step_wise throttling policy. >> This function serves as an arbitrator to set the state of a cooling >> device. It sets the cooling device to the deepest cooling state if >> possible. >> + >> +6. thermal_emergency_poweroff: >> + >> +On an event of critical trip temperature crossing. Thermal framework >> +allows the system to shutdown gracefully by calling orderly_poweroff(). >> +In the event of a failure of orderly_poweroff() to shut down the system >> +we are in danger of keeping the system alive at undesirably high >> +temperatures. To mitigate this high risk scenario we program a work >> +queue to fire after a pre-determined number of seconds to start >> +an emergency shutdown of the device using the kernel_power_off() >> +function. In case kernel_power_off() fails then finally >> +emergency_restart() is called in the worst case. >> + >> +The delay should be carefully profiled so as to give adequate time for >> +orderly_poweroff(). In case of failure of an orderly_poweroff() the >> +emergency poweroff kicks in after the delay has elapsed and shuts down >> +the system. >> + >> +If set to 0 emergency poweroff will not be supported. So a carefully >> +profiled non-zero positive value is a must for emergerncy poweroff to be >> +triggered. >> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig >> index 9347401..2a748a6 100644 >> --- a/drivers/thermal/Kconfig >> +++ b/drivers/thermal/Kconfig >> @@ -15,6 +15,21 @@ menuconfig THERMAL >> >> if THERMAL >> >> +config THERMAL_EMERGENCY_POWEROFF_DELAY_MS >> + int "Emergency poweroff delay in milli-seconds" >> + depends on THERMAL >> + default 0 >> + help >> + The number of milliseconds to delay before emergency >> + poweroff kicks in. The delay should be carefully profiled >> + so as to give adequate time for orderly_poweroff(). In case >> + of failure of an orderly_poweroff() the emergency poweroff >> + kicks in after the delay has elapsed and shuts down the system. >> + >> + If set to 0 emergency poweroff will not be supported. So a carefully >> + profiled non-zero positive value is a must for emergerncy poweroff to be >> + triggered. > > Here is a suggestion for rephrase the above: > > + help > + Thermal subsystem will issue a graceful shutdown when > + critical temperatures are reached using orderly_poweroff(). In > + case of failure of an orderly_poweroff(), the thermal emergency poweroff > + kicks in after a delay has elapsed and shuts down the system. > + This config is number of milliseconds to delay before emergency > + poweroff kicks in. Similarly to the critical trip point, > + the delay should be carefully profiled so as to give adequate > + time for orderly_poweroff() to finish on regular execution. > + If set to 0 emergency poweroff will not be supported. > + > + In doubt, leave as 0. > Okay. >> + >> config THERMAL_HWMON >> bool >> prompt "Expose thermal sensors as hwmon device" >> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c >> index 8337c27..de1f7be 100644 >> --- a/drivers/thermal/thermal_core.c >> +++ b/drivers/thermal/thermal_core.c >> @@ -324,6 +324,54 @@ static void handle_non_critical_trips(struct thermal_zone_device *tz, >> def_governor->throttle(tz, trip); >> } >> >> +/** >> + * thermal_emergency_poweroff_func - emergency poweroff work after a known delay >> + * @work: work_struct associated with the emergency poweroff function >> + * >> + * This function is called in very critical situations to force >> + * a kernel poweroff after a configurable timeout value. >> + */ >> +static void thermal_emergency_poweroff_func(struct work_struct *work) >> +{ >> + /* >> + * We have reached here after the emergency thermal shutdown >> + * Waiting period has expired. This means orderly_poweroff has >> + * not been able to shut off the system for some reason. >> + * Try to shut down the system immediately using kernel_power_off >> + * if populated >> + */ >> + WARN(1, "Attempting kernel_power_off: Temperature too high\n"); >> + kernel_power_off(); >> + >> + /* >> + * Worst of the worst case trigger emergency restart >> + */ >> + WARN(1, "Attempting emergency_restart: Temperature too high\n"); >> + emergency_restart(); >> +} >> + >> +static DECLARE_DELAYED_WORK(thermal_emergency_poweroff_work, >> + thermal_emergency_poweroff_func); >> + >> +/** >> + * thermal_emergency_poweroff - Trigger an emergency system poweroff >> + * >> + * This may be called from any critical situation to trigger a system shutdown >> + * after a known period of time. By default the delay is 0 millisecond >> + */ >> +void thermal_emergency_poweroff(void) >> +{ >> + int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS; >> + /* >> + * poweroff_delay_ms must be a carefully profiled non-zero value. >> + * Its a must for thermal_emergency_poweroff_work to be scheduled >> + */ >> + if (!poweroff_delay_ms) > > This cannot be negative. I think it better suits here: > + if (poweroff_delay_ms <= 0) Sure. I will fix this. > > Let's avoid hidden unsigned round up issues here. > > Despite the above, you can add my > Acked-by: Eduardo Valentin Thanks. I will change this and post it in the v6. > > BR, > > Eduardo Valentin >