wireguard-linux/arch/powerpc/kernel/watchdog.c, branch jd/unified-crypt-queue

powerpc/watchdog: Use hrtimers for per-CPU heartbeat

2019-04-30T01:31:02Z

Using a jiffies timer creates a dependency on the tick_do_timer_cpu incrementing jiffies. If that CPU has locked up and jiffies is not incrementing, the watchdog heartbeat timer for all CPUs stops and creates false positives and confusing warnings on local CPUs, and also causes the SMP detector to stop, so the root cause is never detected. Fix this by using hrtimer based timers for the watchdog heartbeat, like the generic kernel hardlockup detector. Cc: Gautham R. Shenoy Reported-by: Ravikumar Bangoria Signed-off-by: Nicholas Piggin Tested-by: Ravi Bangoria Reported-by: Ravi Bangoria Reviewed-by: Gautham R. Shenoy Signed-off-by: Michael Ellerman

powerpc: NMI IPI make NMI IPIs fully sychronous

2018-07-24T12:03:14Z

There is an asynchronous aspect to smp_send_nmi_ipi. The caller waits for all CPUs to call in to the handler, but it does not wait for completion of the handler. This is a needless complication, so remove it and always wait synchronously. The synchronous wait allows the caller to easily time out and clear the wait for completion (zero nmi_ipi_busy_count) in the case of badly behaved handlers. This would have prevented the recent smp_send_stop NMI IPI bug from causing the system to hang. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman

powerpc/watchdog: provide more data in watchdog messages

2018-05-10T13:25:11Z

Provide timebase and timebase of last heartbeat in watchdog lockup messages. Also provide a stack trace of when a CPU becomes un-stuck, which can be useful -- it could be where irqs are re-enabled, so it may be the end of the critical section which is responsible for the latency which is useful information. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman

powerpc/watchdog: don't update the watchdog timestamp if a lockup is detected

2018-05-10T13:25:11Z

The watchdog heartbeat timestamp is updated when the local heartbeat timer fires (or touch_nmi_watchdog() is called). This is an interesting data point, so don't overwrite it when the soft-NMI interrupt detects a hard lockup. That code came from a pre- merge version to prevent hard lockup messages flood, but that's taken care of with the stuck CPU logic now, so there is no reason to update the heartbeat timestamp here. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman

powerpc/watchdog: fix typo 'can by' to 'can be'

2018-05-10T13:25:05Z

Signed-off-by: Wolfram Sang Signed-off-by: Michael Ellerman

powerpc/watchdog: Print the NIP in soft_nmi_interrupt()

2018-01-28T06:08:29Z

When a CPU detects its locked up via soft_nmi_interrupt() we have pt_regs, so print the regs->nip, which points to where we took the soft-NMI. Signed-off-by: Michael Ellerman

powerpc/watchdog: regs can't be null in soft_nmi_interrupt()

2018-01-28T06:08:28Z

soft_nmi_interrupt() is called directly from the asm exception handling code, which passes regs as a pointer to the stack. So regs can't be NULL, it may be full of junk, but that's a separate problem. Signed-off-by: Michael Ellerman

powerpc/watchdog: Tweak watchdog printks

2018-01-28T06:08:26Z

Use pr_fmt() in the watchdog code, so we don't have to say "Watchdog" so many times. Rather than "CPU:%d" just spell it "CPU %d", "Hard" doesn't need a capital in the middle of a sentence, and "LOCKUP other CPUS" should be "LOCKUP on other CPUS". Also make it clear when a CPU self detects a lockup by spelling it out. Signed-off-by: Michael Ellerman

powerpc/watchdog: improve watchdog comments

2018-01-21T04:06:26Z

The overview comments in the powerpc watchdog are out of date after several iterations and changes of the code. Bring them up to date. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman

powerpc/watchdog: remove arch_trigger_cpumask_backtrace

2018-01-18T04:43:43Z

The powerpc NMI IPIs may not be recoverable if they are taken in some sections of code, and also there have been and still are issues with taking NMIs (in KVM guest code, in firmware, etc) which makes them a bit dangerous to use. Generic code like softlockup detector and rcu stall detectors really hammer on trigger_*_backtrace, which has lead to further problems because we've implemented it with the NMI. So stop providing NMI backtraces for now. Importantly, the powerpc code uses NMI IPIs in crash/debug, and the SMP hardlockup watchdog. So if the softlockup and rcu hang detection traces are not being printed because the CPU is stuck with interrupts off, then the hard lockup watchdog should get it with the NMI IPI. Fixes: 2104180a5369 ("powerpc/64s: implement arch-specific hardlockup watchdog") Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman