The change adds a simple watchdog pretimeout framework infrastructure, its purpose is to allow users to select a desired handling of watchdog pretimeout events, which may be generated by a watchdog driver. The idea of adding this kind of a framework appeared after reviewing several attempts to add hardcoded pretimeout event handling to some watchdog driver and after a discussion with Guenter, see https://lkml.org/lkml/2015/11/4/346 Watchdogs with WDIOF_PRETIMEOUT capability now may have three device attributes in sysfs: read only pretimeout value attribute, read/write pretimeout_governor attribute, read only pretimeout_available_governors attribute. To throw a pretimeout event for further processing a watchdog driver should call exported watchdog_notify_pretimeout(wdd) interface. In addition to the framework two simple watchdog pretimeout governors are added for review: noop (default) and panic. This series is based on current Wim's watchdog/master branch, also I took the liberty of adding commit message tags provided by Wolfram and Guenter for v5, because the only functional change between v5 and v6 is quite trivial, please feel free to revoke or confirm the tags: diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h index c776debde228..35a4d8185b51 100644 --- a/include/linux/watchdog.h +++ b/include/linux/watchdog.h @@ -194,7 +194,7 @@ void watchdog_notify_pretimeout(struct watchdog_device *wdd); #else static inline void watchdog_notify_pretimeout(struct watchdog_device *wdd) { - panic("watchdog pretimeout event\n"); + pr_alert("watchdog%d: pretimeout event\n", wdd->id); } #endif Changes from v5 to v6: * rebased on top of Wim's watchdog/master branch for v4.9 release, 3 commits are already applied, thus they are dropped from the series, * swapped panic and noop governors per Wim's request, now noop action on pretimeout is set by default (same as in v1 of the series), * slightly extended a commit message of the panic pretimeout governor, * added reviewed-by and tested-by tags given by Wolfram and Guenter. Changes from v4 to v5: * fixed in source tree compilation issue, thanks to Wolfram * replaced strncmp() with more suitable sysfs_streq() to compare strings passed over sysfs (Wolfram) * added Wolfram's implementation of pretimeout to softdog driver * added watchdog pretimeout support to iMX2+ driver * minor whitespace issue fixes reported by checkpatch Changes from v3 to v4 : * took Wolfram's more advanced flavour of "watchdog: add set_pretimeout interface" change, which is based on originally written by Robin Gong code (Wolfram) * documented new watchdog_notify_pretimeout() function for developers of watchdog device drivers (Guenter) * reordered logical operations in wdt_is_visible() for better clarity (Guenter) * if watchdog pretimeout governor is not registered return empty string on reading "pretimeout_governor" device attribute, however with the default governor built-in this should never happen on practice (Guenter) * removed a number of sanity checks from functions which are assumed to be exported, callers are expected to write correct code, also this fixes one bug in watchdog_register_governor() noticed by Guenter (Guenter) * reworded some commit messages (Guenter) * moved registration of watchdog pretimeout event by from watchdog_core.c to watchdog_dev.c (Wolfram) * from the series removed support of potentially sleeping governors (Wolfram) * removed "panic panic" duplication in a user's message (Wolfram) * report watchdog name in a message given by noop governor (Wolfram) * exploiting the fact that there is only one default governor selected at build time allows to remove .is_default from "struct governor_priv" and find_default_governor() helper function, this is a change against complete version v2 * by unloading some assigned non-default governor a watchdog device falls back to default governor, this allows to avoid complicated module locking scheme by module owners, this is a change against completeversion v2 * to avoid spreading of watchdog device "struct device" operations while adding device attributes by watchdog_pretimeout_governor_[gs]et() and watchdog_pretimeout_available_governors_get() functions called from watchdog_dev.c, this is a change against complete version v2 * split the main change into 3 to hopefully enlighten review process: 1) default governor support only, 2) selectable by a user governor in runtime, 3) added pretimeout_available_governors attribute * fixed a list element deregistration bug Changes from v2 to v3: * from watchdog_pretimeout.c removed all features mentioned above * rebased panic and noop governors on top of the simplified watchdog pretimeout framework * added 2 rebased and cleaned up changes done by Robin Gong to the series, Robin's changes allow to test the series, if some individual watchdog driver adds WDIOF_PRETIMEOUT support and calls watchdog_notify_pretimeout(), for example Robin implemented the feature for imx2+ watchdog driver * added pretimeout value display over sysfs for WDIOF_PRETIMEOUT capable watchdog devices * moved sysfs device attributes to watchdog_dev.c, this required to add exported watchdog_pretimeout_governor_name() interface * if pretimeout framework is not selected, then pretimeout event ends up in kernel panic -- this behaviour as a default one was asked by Guenter * due to removal of support to sleeing governors removed userspace notification pretimeout governor from the series * minor clean-ups and adjustments Changes from v1 to v2, thanks to Guenter for review and discussion: * removed re-ping pretimeout governor, the functionality is supposed to be covered by the pending infrastructure enhancements, * removed watchdog driver specific pretimeout governor, at the moment it is not expected to add driver specific handlers, * reordered governors, panic comes in the first place, * removed framework private bits from struct watchdog_governor, * centralized compile-time selection of a default governor in watchdog_pretimeout.h, * added can_sleep option, now only sleeping governors (e.g. userspace) will be executed in a special workqueue, * changed fallback logic, if a governor in use is removed, now this situation is not possible, because in use governors have non-zero module refcount, * slightly improved description of the governors in Kconfig. Vladimir Zapolskiy (6): watchdog: add watchdog pretimeout governor framework watchdog: pretimeout: add noop pretimeout governor watchdog: pretimeout: add panic pretimeout governor watchdog: pretimeout: add option to select a pretimeout governor in runtime watchdog: pretimeout: add pretimeout_available_governors attribute watchdog: imx2_wdt: add pretimeout function support Wolfram Sang (1): watchdog: softdog: implement pretimeout support Documentation/watchdog/watchdog-kernel-api.txt | 13 ++ drivers/watchdog/Kconfig | 49 ++++++ drivers/watchdog/Makefile | 8 +- drivers/watchdog/imx2_wdt.c | 48 ++++++ drivers/watchdog/pretimeout_noop.c | 47 ++++++ drivers/watchdog/pretimeout_panic.c | 47 ++++++ drivers/watchdog/softdog.c | 22 ++- drivers/watchdog/watchdog_dev.c | 45 +++++ drivers/watchdog/watchdog_pretimeout.c | 220 +++++++++++++++++++++++++ drivers/watchdog/watchdog_pretimeout.h | 60 +++++++ include/linux/watchdog.h | 13 ++ 11 files changed, 570 insertions(+), 2 deletions(-) create mode 100644 drivers/watchdog/pretimeout_noop.c create mode 100644 drivers/watchdog/pretimeout_panic.c create mode 100644 drivers/watchdog/watchdog_pretimeout.c create mode 100644 drivers/watchdog/watchdog_pretimeout.h -- 2.8.1 -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
