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6687659568
linux/kernel
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Davidlohr Bueso 6687659568 locking/pvqspinlock: Fix division by zero in qstat_read() 
While playing with the qstat statistics (in <debugfs>/qlockstat/) I ran into
the following splat on a VM when opening pv_hash_hops:

  divide error: 0000 [#1] SMP
  ...
  RIP: 0010:[<ffffffff810b61fe>]  [<ffffffff810b61fe>] qstat_read+0x12e/0x1e0
  ...
  Call Trace:
    [<ffffffff811cad7c>] ? mem_cgroup_commit_charge+0x6c/0xd0
    [<ffffffff8119750c>] ? page_add_new_anon_rmap+0x8c/0xd0
    [<ffffffff8118d3b9>] ? handle_mm_fault+0x1439/0x1b40
    [<ffffffff811937a9>] ? do_mmap+0x449/0x550
    [<ffffffff811d3de3>] ? __vfs_read+0x23/0xd0
    [<ffffffff811d4ab2>] ? rw_verify_area+0x52/0xd0
    [<ffffffff811d4bb1>] ? vfs_read+0x81/0x120
    [<ffffffff811d5f12>] ? SyS_read+0x42/0xa0
    [<ffffffff815720f6>] ? entry_SYSCALL_64_fastpath+0x1e/0xa8

Fix this by verifying that qstat_pv_kick_unlock is in fact non-zero,
similarly to what the qstat_pv_latency_wake case does, as if nothing
else, this can come from resetting the statistics, thus having 0 kicks
should be quite valid in this context.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Waiman Long <Waiman.Long@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Cc: waiman.long@hpe.com
Link: http://lkml.kernel.org/r/1460961103-24953-1-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-19 10:49:19 +02:00
..
bpf bpf: add missing map_flags to bpf_map_show_fdinfo 2016-03-25 11:36:41 -04:00
configs
debug mm/init: Add 'rodata=off' boot cmdline parameter to disable read-only kernel mappings 2016-02-22 08:51:37 +01:00
events Merge branch 'PAGE_CACHE_SIZE-removal' 2016-04-04 10:50:24 -07:00
gcov gcov: use within_module() helper. 2015-12-04 22:46:25 +01:00
irq kernel/...: convert pr_warning to pr_warn 2016-03-22 15:36:02 -07:00
livepatch livepatch/module: remove livepatch module notifier 2016-03-17 09:45:10 +01:00
locking locking/pvqspinlock: Fix division by zero in qstat_read() 2016-04-19 10:49:19 +02:00
power Power management and ACPI material for v4.6-rc1, part 2 2016-03-24 22:59:58 -07:00
printk printk: add clear_idx symbol to vmcoreinfo 2016-03-17 15:09:34 -07:00
rcu kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
sched locking/atomic, sched: Unexport fetch_or() 2016-03-29 11:52:11 +02:00
time timers/nohz: Convert tick dependency mask to atomic_t 2016-03-29 11:52:11 +02:00
trace arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
.gitignore
acct.c
async.c
audit_fsnotify.c wrappers for ->i_mutex access 2016-01-22 18:04:28 -05:00
audit_tree.c
audit_watch.c Merge branch 'stable-4.6' of git://git.infradead.org/users/pcmoore/audit 2016-03-19 17:52:49 -07:00
audit.c Merge branch 'stable-4.6' of git://git.infradead.org/users/pcmoore/audit 2016-03-19 17:52:49 -07:00
audit.h security: Make inode argument of inode_getsecid non-const 2015-12-24 11:09:39 -05:00
auditfilter.c audit: Fix typo in comment 2016-02-08 11:25:39 -05:00
auditsc.c auditsc: for seccomp events, log syscall compat state using in_compat_syscall 2016-03-22 15:36:02 -07:00
backtracetest.c
bounds.c
capability.c
cgroup_freezer.c
cgroup_pids.c cgroup_pids: fix a typo. 2015-12-14 14:54:37 -05:00
cgroup.c Merge branch 'for-4.6-ns' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2016-03-21 10:05:13 -07:00
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c cpu/hotplug: Document states better 2016-03-12 20:57:38 +01:00
cpuset.c Merge branch 'for-4.6-ns' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2016-03-21 10:05:13 -07:00
crash_dump.c
cred.c kmemcg: account certain kmem allocations to memcg 2016-01-14 16:00:49 -08:00
delayacct.c kmemcg: account certain kmem allocations to memcg 2016-01-14 16:00:49 -08:00
dma.c
elfcore.c
exec_domain.c
exit.c oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space 2016-03-25 16:37:42 -07:00
extable.c
fork.c kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
freezer.c
futex_compat.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-01-20 17:09:18 -08:00
futex.c futex: Replace barrier() in unqueue_me() with READ_ONCE() 2016-03-08 17:04:02 +01:00
groups.c
hung_task.c kernel/hung_task.c: use timeout diff when timeout is updated 2016-03-22 15:36:02 -07:00
irq_work.c
jump_label.c
kallsyms.c kallsyms: add support for relative offsets in kallsyms address table 2016-03-15 16:55:16 -07:00
kcmp.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-01-20 17:09:18 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
kexec_core.c kexec: Set IORESOURCE_SYSTEM_RAM for System RAM 2016-01-30 09:49:57 +01:00
kexec_file.c Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2016-03-17 11:33:45 -07:00
kexec_internal.h kexec: move some memembers and definitions within the scope of CONFIG_KEXEC_FILE 2016-01-20 17:09:18 -08:00
kexec.c kexec: set KEXEC_TYPE_CRASH before sanity_check_segment_list() 2016-01-20 17:09:18 -08:00
kmod.c
kprobes.c
ksysfs.c rcu: Remove TINY_RCU bloat from pointless boot parameters 2015-12-07 16:59:37 -08:00
kthread.c
latencytop.c sched/debug: Make schedstats a runtime tunable that is disabled by default 2016-02-09 11:54:23 +01:00
Makefile kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
membarrier.c
memremap.c memremap: add MEMREMAP_WC flag 2016-03-22 15:36:02 -07:00
module_signing.c X.509: Make algo identifiers text instead of enum 2016-03-03 21:49:27 +00:00
module-internal.h
module.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching 2016-03-17 21:46:32 -07:00
notifier.c
nsproxy.c cgroup: introduce cgroup namespaces 2016-02-16 13:04:58 -05:00
padata.c
panic.c panic: change nmi_panic from macro to function 2016-03-22 15:36:02 -07:00
params.c
pid_namespace.c
pid.c Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-01-31 15:44:04 -08:00
profile.c profile: hide unused functions when !CONFIG_PROC_FS 2016-03-22 15:36:02 -07:00
ptrace.c ptrace: change __ptrace_unlink() to clear ->ptrace under ->siglock 2016-03-22 15:36:02 -07:00
range.c
reboot.c
relay.c wrappers for ->i_mutex access 2016-01-22 18:04:28 -05:00
resource.c /proc/iomem: only expose physical resource addresses to privileged users 2016-04-14 12:56:09 -07:00
seccomp.c seccomp: check in_compat_syscall, not is_compat_task, in strict mode 2016-03-22 15:36:02 -07:00
signal.c kernel/signal.c: add compile-time check for __ARCH_SI_PREAMBLE_SIZE 2016-03-22 15:36:02 -07:00
smp.c Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-03-15 13:50:29 -07:00
smpboot.c cpu/hotplug: Unpark smpboot threads from the state machine 2016-03-01 20:36:56 +01:00
smpboot.h cpu/hotplug: Create hotplug threads 2016-03-01 20:36:56 +01:00
softirq.c arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
stacktrace.c
stop_machine.c kernel/stop_machine.c: remove CONFIG_SMP dependencies 2016-01-16 11:17:24 -08:00
sys_ni.c
sys.c timer: convert timer_slack_ns from unsigned long to u64 2016-03-17 15:09:34 -07:00
sysctl_binary.c fs/coredump: prevent fsuid=0 dumps into user-controlled directories 2016-03-22 15:36:02 -07:00
sysctl.c mm: scale kswapd watermarks in proportion to memory 2016-03-17 15:09:34 -07:00
task_work.c
taskstats.c
test_kprobes.c
torture.c
tracepoint.c kernel/...: convert pr_warning to pr_warn 2016-03-22 15:36:02 -07:00
tsacct.c time, acct: Drop irq save & restore from __acct_update_integrals() 2016-02-29 09:53:09 +01:00
uid16.c
up.c
user_namespace.c kernel/*: switch to memdup_user_nul() 2016-01-04 10:27:55 -05:00
user-return-notifier.c
user.c
utsname_sysctl.c
utsname.c
watchdog.c watchdog: don't run proc_watchdog_update if new value is same as old 2016-03-17 15:09:34 -07:00
workqueue_internal.h sched/core: Get rid of 'cpu' argument in wq_worker_sleeping() 2016-03-02 10:28:47 -05:00
workqueue.c Merge branch 'for-4.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2016-03-18 20:05:39 -07:00