The following two patches solve an issue reported by Steffen Trumtrar and Tim Sander to the linux-rt-users mailing list. Namely, the wakeup of the watchdogd thread being starved by an RT task due to the hrtimer deferral through ktimersoftd (on PREEMPT_RT_FULL).
The first patch adjusts the kthread_worker locking to make use of a raw spinlock, making it suitable for work item queueing from hardirq context on PREEMPT_RT. This patch can be applied directly to mainline without any functional change. The second patch adjusts the hrtimer used by the watchdog core to be a _HARD timer (and thus not deferred through ktimersoftd w/ PREEMPT_RT). This patch depends on hrtimer patches carried in the RT patch, and so should therefore land there. Cc: Guenter Roeck <[email protected]> Cc: Steffen Trumtrar <[email protected]> Cc: Tim Sander <[email protected]> Julia Cartwright (2): kthread: convert worker lock to raw spinlock watchdog, rt: prevent deferral of watchdogd wakeup drivers/watchdog/watchdog_dev.c | 2 +- include/linux/kthread.h | 2 +- kernel/kthread.c | 42 ++++++++++++++++----------------- 3 files changed, 23 insertions(+), 23 deletions(-) -- 2.18.0
