linux/kernel/watchdog.c, branch v3.19

Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

2014-10-15T05:48:18Z

Pull percpu consistent-ops changes from Tejun Heo: "Way back, before the current percpu allocator was implemented, static and dynamic percpu memory areas were allocated and handled separately and had their own accessors. The distinction has been gone for many years now; however, the now duplicate two sets of accessors remained with the pointer based ones - this_cpu_*() - evolving various other operations over time. During the process, we also accumulated other inconsistent operations. This pull request contains Christoph's patches to clean up the duplicate accessor situation. __get_cpu_var() uses are replaced with with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr(). Unfortunately, the former sometimes is tricky thanks to C being a bit messy with the distinction between lvalues and pointers, which led to a rather ugly solution for cpumask_var_t involving the introduction of this_cpu_cpumask_var_ptr(). This converts most of the uses but not all. Christoph will follow up with the remaining conversions in this merge window and hopefully remove the obsolete accessors" * 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits) irqchip: Properly fetch the per cpu offset percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write. percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t Revert "powerpc: Replace __get_cpu_var uses" percpu: Remove __this_cpu_ptr clocksource: Replace __this_cpu_ptr with raw_cpu_ptr sparc: Replace __get_cpu_var uses avr32: Replace __get_cpu_var with __this_cpu_write blackfin: Replace __get_cpu_var uses tile: Use this_cpu_ptr() for hardware counters tile: Replace __get_cpu_var uses powerpc: Replace __get_cpu_var uses alpha: Replace __get_cpu_var ia64: Replace __get_cpu_var uses s390: cio driver &__get_cpu_var replacements s390: Replace __get_cpu_var uses mips: Replace __get_cpu_var uses MIPS: Replace __get_cpu_var uses in FPU emulator. arm: Replace __this_cpu_ptr with raw_cpu_ptr ...

kernel/watchdog.c: control hard lockup detection default

2014-10-14T00:18:27Z

In some cases we don't want hard lockup detection enabled by default. An example is when running as a guest. Introduce watchdog_enable_hardlockup_detector(bool) allowing those cases to disable hard lockup detection. This must be executed early by the boot processor from e.g. smp_prepare_boot_cpu, in order to allow kernel command line arguments to override it, as well as to avoid hard lockup detection being enabled before we've had a chance to indicate that it's unwanted. In summary, initial boot: default=enabled smp_prepare_boot_cpu watchdog_enable_hardlockup_detector(false): default=disabled cmdline has 'nmi_watchdog=1': default=enabled The running kernel still has the ability to enable/disable at any time with /proc/sys/kernel/nmi_watchdog us usual. However even when the default has been overridden /proc/sys/kernel/nmi_watchdog will initially show '1'. To truly turn it on one must disable/enable it, i.e. echo 0 > /proc/sys/kernel/nmi_watchdog echo 1 > /proc/sys/kernel/nmi_watchdog This patch will be immediately useful for KVM with the next patch of this series. Other hypervisor guest types may find it useful as well. [akpm@linux-foundation.org: fix build] [dzickus@redhat.com: fix compile issues on sparc] Signed-off-by: Ulrich Obergfell Signed-off-by: Andrew Jones Signed-off-by: Don Zickus Signed-off-by: Don Zickus Cc: Stephen Rothwell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'perf-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-10-13T14:10:06Z

Pull watchdog fixes from Ingo Molnar: "Two small watchdog subsystem fixes" * 'perf-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: watchdog: Fix print-once on enable watchdog: Remove unnecessary header files

softlockup: make detector be aware of task switch of processes hogging cpu

2014-10-10T02:25:48Z

For now, soft lockup detector warns once for each case of process softlockup. But the thread 'watchdog/n' may not always get the cpu at the time slot between the task switch of two processes hogging that cpu to reset soft_watchdog_warn. An example would be two processes hogging the cpu. Process A causes the softlockup warning and is killed manually by a user. Process B immediately becomes the new process hogging the cpu preventing the softlockup code from resetting the soft_watchdog_warn variable. This case is a false negative of "warn only once for a process", as there may be a different process that is going to hog the cpu. Resolve this by saving/checking the task pointer of the hogging process and use that to reset soft_watchdog_warn too. [dzickus@redhat.com: update comment] Signed-off-by: chai wen Signed-off-by: Don Zickus Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

watchdog: Replace __raw_get_cpu_var uses

2014-08-26T17:45:46Z

Most of these are the uses of &__raw_get_cpu_var for address calculation. touch_softlockup_watchdog_sync() uses __raw_get_cpu_var to write to per cpu variables. Use __this_cpu_write instead. Cc: Wim Van Sebroeck Cc: linux-watchdog@vger.kernel.org Signed-off-by: Christoph Lameter Signed-off-by: Tejun Heo

watchdog: Fix print-once on enable

2014-08-18T09:17:46Z

This patch avoids printing the message 'enabled on all CPUs, ...' multiple times. For example, the issue can occur in the following scenario: 1) watchdog_nmi_enable() fails to enable PMU counters and sets cpu0_err. 2) 'echo [0|1] > /proc/sys/kernel/nmi_watchdog' is executed to disable and re-enable the watchdog mechanism 'on the fly'. 3) If watchdog_nmi_enable() succeeds to enable PMU counters, each CPU will print the message because step1 left behind a non-zero cpu0_err. if (!IS_ERR(event)) { if (cpu == 0 || cpu0_err) pr_info("enabled on all CPUs, ...") The patch avoids this by clearing cpu0_err in watchdog_nmi_disable(). Signed-off-by: Ulrich Obergfell Signed-off-by: Andrew Jones Signed-off-by: Don Zickus Cc: pbonzini@redhat.com Link: http://lkml.kernel.org/r/1407768567-171794-4-git-send-email-dzickus@redhat.com [ Applied small cleanups. ] Signed-off-by: Ingo Molnar

watchdog: Remove unnecessary header files

2014-08-18T09:17:46Z

Signed-off-by: chai wen Signed-off-by: Don Zickus Cc: pbonzini@redhat.com Link: http://lkml.kernel.org/r/1407768567-171794-2-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar

panic: add TAINT_SOFTLOCKUP

2014-08-08T22:57:24Z

This taint flag will be set if the system has ever entered a softlockup state. Similar to TAINT_WARN it is useful to know whether or not the system has been in a softlockup state when debugging. [akpm@linux-foundation.org: apply the taint before calling panic()] Signed-off-by: Josh Hunt Cc: Jason Baron Cc: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/watchdog.c: convert printk/pr_warning to pr_foo()

2014-08-07T01:01:13Z

Replace some obsolete functions. Signed-off-by: Fabian Frederick Cc: Frederic Weisbecker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/watchdog.c: print traces for all cpus on lockup detection

2014-06-23T23:47:44Z

A 'softlockup' is defined as a bug that causes the kernel to loop in kernel mode for more than a predefined period to time, without giving other tasks a chance to run. Currently, upon detection of this condition by the per-cpu watchdog task, debug information (including a stack trace) is sent to the system log. On some occasions, we have observed that the "victim" rather than the actual "culprit" (i.e. the owner/holder of the contended resource) is reported to the user. Often this information has proven to be insufficient to assist debugging efforts. To avoid loss of useful debug information, for architectures which support NMI, this patch makes it possible to improve soft lockup reporting. This is accomplished by issuing an NMI to each cpu to obtain a stack trace. If NMI is not supported we just revert back to the old method. A sysctl and boot-time parameter is available to toggle this feature. [dzickus@redhat.com: add CONFIG_SMP in certain areas] [akpm@linux-foundation.org: additional CONFIG_SMP=n optimisations] [mq@suse.cz: fix warning] Signed-off-by: Aaron Tomlin Signed-off-by: Don Zickus Cc: David S. Miller Cc: Mateusz Guzik Cc: Oleg Nesterov Signed-off-by: Jan Moskyto Matejka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds