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powerpc/64s: implement arch-specific hardlockup watchdog

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Implement an arch-speicfic watchdog rather than use the perf-based
hardlockup detector.

The new watchdog takes the soft-NMI directly, rather than going through
perf.  Perf interrupts are to be made maskable in future, so that would
prevent the perf detector from working in those regions.

Additionally, implement a SMP based detector where all CPUs watch one
another by pinging a shared cpumask.  This is because powerpc Book3S
does not have a true periodic local NMI, but some platforms do implement
a true NMI IPI.

If a CPU is stuck with interrupts hard disabled, the soft-NMI watchdog
does not work, but the SMP watchdog will.  Even on platforms without a
true NMI IPI to get a good trace from the stuck CPU, other CPUs will
notice the lockup sufficiently to report it and panic.

[npiggin@gmail.com: honor watchdog disable at boot/hotplug]
  Link: http://lkml.kernel.org/r/20170621001346.5bb337c9@roar.ozlabs.ibm.com
[npiggin@gmail.com: fix false positive warning at CPU unplug]
  Link: http://lkml.kernel.org/r/20170630080740.20766-1-npiggin@gmail.com
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170616065715.18390-6-npiggin@gmail.com
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Tested-by: Babu Moger <babu.moger@oracle.com>	[sparc]
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nicholas Piggin 2017-07-12 14:35:52 -07:00 committed by Linus Torvalds
parent a10a842ff8
commit 2104180a53
9 changed files with 458 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/powerpc/Kconfig
View File

@ -82,7 +82,7 @@ config NR_IRQS
config NMI_IPI
bool
depends on SMP && (DEBUGGER || KEXEC_CORE)
depends on SMP && (DEBUGGER || KEXEC_CORE || HARDLOCKUP_DETECTOR)
default y
config STACKTRACE_SUPPORT
@ -192,12 +192,13 @@ config PPC
select HAVE_MEMBLOCK
select HAVE_MEMBLOCK_NODE_MAP
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_NMI if PERF_EVENTS
select HAVE_NMI if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
select HAVE_HARDLOCKUP_DETECTOR_ARCH if (PPC64 && PPC_BOOK3S)
select HAVE_OPROFILE
select HAVE_OPTPROBES if PPC64
select HAVE_PERF_EVENTS
select HAVE_PERF_EVENTS_NMI if PPC64
select HAVE_HARDLOCKUP_DETECTOR_PERF if HAVE_PERF_EVENTS_NMI
select HAVE_HARDLOCKUP_DETECTOR_PERF if HAVE_PERF_EVENTS_NMI && !HAVE_HARDLOCKUP_DETECTOR_ARCH
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select HAVE_RCU_TABLE_FREE if SMP

11
arch/powerpc/include/asm/nmi.h
View File

@ -1,4 +1,15 @@
#ifndef _ASM_NMI_H
#define _ASM_NMI_H
#ifdef CONFIG_HARDLOCKUP_DETECTOR
extern void arch_touch_nmi_watchdog(void);
extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
bool exclude_self);
#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
#else
static inline void arch_touch_nmi_watchdog(void) {}
#endif
#endif /* _ASM_NMI_H */

2
arch/powerpc/include/asm/smp.h
View File

@ -55,6 +55,8 @@ struct smp_ops_t {
int (*cpu_bootable)(unsigned int nr);
};
extern void smp_flush_nmi_ipi(u64 delay_us);
extern int smp_send_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us);
extern void smp_send_debugger_break(void);
extern void start_secondary_resume(void);
extern void smp_generic_give_timebase(void);

1
arch/powerpc/kernel/Makefile
View File

@ -38,6 +38,7 @@ obj-$(CONFIG_PPC64) += setup_64.o sys_ppc32.o \
signal_64.o ptrace32.o \
paca.o nvram_64.o firmware.o
obj-$(CONFIG_VDSO32) += vdso32/
obj-$(CONFIG_HARDLOCKUP_DETECTOR) += watchdog.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_ppc970.o cpu_setup_pa6t.o
obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_power.o

30
arch/powerpc/kernel/exceptions-64s.S
View File

@ -1314,6 +1314,31 @@ EXC_REAL_NONE(0x1800, 0x100)
EXC_VIRT_NONE(0x5800, 0x100)
#endif
#if defined(CONFIG_HARDLOCKUP_DETECTOR) && defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH)
#define MASKED_DEC_HANDLER_LABEL 3f
#define MASKED_DEC_HANDLER(_H) \
3: /* soft-nmi */ \
std r12,PACA_EXGEN+EX_R12(r13); \
GET_SCRATCH0(r10); \
std r10,PACA_EXGEN+EX_R13(r13); \
EXCEPTION_PROLOG_PSERIES_1(soft_nmi_common, _H)
EXC_COMMON_BEGIN(soft_nmi_common)
mr r10,r1
ld r1,PACAEMERGSP(r13)
ld r1,PACA_NMI_EMERG_SP(r13)
subi r1,r1,INT_FRAME_SIZE
EXCEPTION_COMMON_NORET_STACK(PACA_EXGEN, 0x900,
system_reset, soft_nmi_interrupt,
ADD_NVGPRS;ADD_RECONCILE)
b ret_from_except
#else
#define MASKED_DEC_HANDLER_LABEL 2f /* normal return */
#define MASKED_DEC_HANDLER(_H)
#endif
/*
* An interrupt came in while soft-disabled. We set paca->irq_happened, then:
@ -1336,7 +1361,7 @@ masked_##_H##interrupt: \
lis r10,0x7fff; \
ori r10,r10,0xffff; \
mtspr SPRN_DEC,r10; \
b 2f; \
b MASKED_DEC_HANDLER_LABEL; \
1: cmpwi r10,PACA_IRQ_DBELL; \
beq 2f; \
cmpwi r10,PACA_IRQ_HMI; \
@ -1351,7 +1376,8 @@ masked_##_H##interrupt: \
ld r11,PACA_EXGEN+EX_R11(r13); \
GET_SCRATCH0(r13); \
##_H##rfid; \
b .
b .; \
MASKED_DEC_HANDLER(_H)
/*
* Real mode exceptions actually use this too, but alternate

7
arch/powerpc/kernel/kvm.c
View File

@ -25,6 +25,7 @@
#include <linux/kvm_para.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/nmi.h> /* hardlockup_detector_disable() */
#include <asm/reg.h>
#include <asm/sections.h>
@ -718,6 +719,12 @@ static __init void kvm_free_tmp(void)
static int __init kvm_guest_init(void)
{
/*
* The hardlockup detector is likely to get false positives in
* KVM guests, so disable it by default.
*/
hardlockup_detector_disable();
if (!kvm_para_available())
goto free_tmp;

19
arch/powerpc/kernel/setup_64.c
View File

@ -751,22 +751,3 @@ unsigned long memory_block_size_bytes(void)
struct ppc_pci_io ppc_pci_io;
EXPORT_SYMBOL(ppc_pci_io);
#endif
#ifdef CONFIG_HARDLOCKUP_DETECTOR_PERF
u64 hw_nmi_get_sample_period(int watchdog_thresh)
{
return ppc_proc_freq * watchdog_thresh;
}
/*
* The hardlockup detector breaks PMU event based branches and is likely
* to get false positives in KVM guests, so disable it by default.
*/
static int __init disable_hardlockup_detector(void)
{
hardlockup_detector_disable();
return 0;
}
early_initcall(disable_hardlockup_detector);
#endif

20
arch/powerpc/kernel/smp.c
View File

@ -435,13 +435,31 @@ static void do_smp_send_nmi_ipi(int cpu)
}
}
void smp_flush_nmi_ipi(u64 delay_us)
{
unsigned long flags;
nmi_ipi_lock_start(&flags);
while (nmi_ipi_busy_count) {
nmi_ipi_unlock_end(&flags);
udelay(1);
if (delay_us) {
delay_us--;
if (!delay_us)
return;
}
nmi_ipi_lock_start(&flags);
}
nmi_ipi_unlock_end(&flags);
}
/*
* - cpu is the target CPU (must not be this CPU), or NMI_IPI_ALL_OTHERS.
* - fn is the target callback function.
* - delay_us > 0 is the delay before giving up waiting for targets to
* enter the handler, == 0 specifies indefinite delay.
*/
static int smp_send_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us)
int smp_send_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us)
{
unsigned long flags;
int me = raw_smp_processor_id();

386
arch/powerpc/kernel/watchdog.c Normal file
View File

@ -0,0 +1,386 @@
/*
* Watchdog support on powerpc systems.
*
* Copyright 2017, IBM Corporation.
*
* This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
*/
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/nmi.h>
#include <linux/module.h>
#include <linux/export.h>
#include <linux/kprobes.h>
#include <linux/hardirq.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/kdebug.h>
#include <linux/sched/debug.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <asm/paca.h>
/*
* The watchdog has a simple timer that runs on each CPU, once per timer
* period. This is the heartbeat.
*
* Then there are checks to see if the heartbeat has not triggered on a CPU
* for the panic timeout period. Currently the watchdog only supports an
* SMP check, so the heartbeat only turns on when we have 2 or more CPUs.
*
* This is not an NMI watchdog, but Linux uses that name for a generic
* watchdog in some cases, so NMI gets used in some places.
*/
static cpumask_t wd_cpus_enabled __read_mostly;
static u64 wd_panic_timeout_tb __read_mostly; /* timebase ticks until panic */
static u64 wd_smp_panic_timeout_tb __read_mostly; /* panic other CPUs */
static u64 wd_timer_period_ms __read_mostly; /* interval between heartbeat */
static DEFINE_PER_CPU(struct timer_list, wd_timer);
static DEFINE_PER_CPU(u64, wd_timer_tb);
/*
* These are for the SMP checker. CPUs clear their pending bit in their
* heartbeat. If the bitmask becomes empty, the time is noted and the
* bitmask is refilled.
*
* All CPUs clear their bit in the pending mask every timer period.
* Once all have cleared, the time is noted and the bits are reset.
* If the time since all clear was greater than the panic timeout,
* we can panic with the list of stuck CPUs.
*
* This will work best with NMI IPIs for crash code so the stuck CPUs
* can be pulled out to get their backtraces.
*/
static unsigned long __wd_smp_lock;
static cpumask_t wd_smp_cpus_pending;
static cpumask_t wd_smp_cpus_stuck;
static u64 wd_smp_last_reset_tb;
static inline void wd_smp_lock(unsigned long *flags)
{
/*
* Avoid locking layers if possible.
* This may be called from low level interrupt handlers at some
* point in future.
*/
local_irq_save(*flags);
while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock)))
cpu_relax();
}
static inline void wd_smp_unlock(unsigned long *flags)
{
clear_bit_unlock(0, &__wd_smp_lock);
local_irq_restore(*flags);
}
static void wd_lockup_ipi(struct pt_regs *regs)
{
pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
print_modules();
print_irqtrace_events(current);
if (regs)
show_regs(regs);
else
dump_stack();
if (hardlockup_panic)
nmi_panic(regs, "Hard LOCKUP");
}
static void set_cpu_stuck(int cpu, u64 tb)
{
cpumask_set_cpu(cpu, &wd_smp_cpus_stuck);
cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
if (cpumask_empty(&wd_smp_cpus_pending)) {
wd_smp_last_reset_tb = tb;
cpumask_andnot(&wd_smp_cpus_pending,
&wd_cpus_enabled,
&wd_smp_cpus_stuck);
}
}
static void watchdog_smp_panic(int cpu, u64 tb)
{
unsigned long flags;
int c;
wd_smp_lock(&flags);
/* Double check some things under lock */
if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
goto out;
if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
goto out;
if (cpumask_weight(&wd_smp_cpus_pending) == 0)
goto out;
pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
cpu, cpumask_pr_args(&wd_smp_cpus_pending));
/*
* Try to trigger the stuck CPUs.
*/
for_each_cpu(c, &wd_smp_cpus_pending) {
if (c == cpu)
continue;
smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
}
smp_flush_nmi_ipi(1000000);
/* Take the stuck CPU out of the watch group */
for_each_cpu(c, &wd_smp_cpus_pending)
set_cpu_stuck(c, tb);
out:
wd_smp_unlock(&flags);
printk_safe_flush();
/*
* printk_safe_flush() seems to require another print
* before anything actually goes out to console.
*/
if (sysctl_hardlockup_all_cpu_backtrace)
trigger_allbutself_cpu_backtrace();
if (hardlockup_panic)
nmi_panic(NULL, "Hard LOCKUP");
}
static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
{
if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
unsigned long flags;
pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
wd_smp_lock(&flags);
cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
wd_smp_unlock(&flags);
}
return;
}
cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
if (cpumask_empty(&wd_smp_cpus_pending)) {
unsigned long flags;
wd_smp_lock(&flags);
if (cpumask_empty(&wd_smp_cpus_pending)) {
wd_smp_last_reset_tb = tb;
cpumask_andnot(&wd_smp_cpus_pending,
&wd_cpus_enabled,
&wd_smp_cpus_stuck);
}
wd_smp_unlock(&flags);
}
}
static void watchdog_timer_interrupt(int cpu)
{
u64 tb = get_tb();
per_cpu(wd_timer_tb, cpu) = tb;
wd_smp_clear_cpu_pending(cpu, tb);
if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb)
watchdog_smp_panic(cpu, tb);
}
void soft_nmi_interrupt(struct pt_regs *regs)
{
unsigned long flags;
int cpu = raw_smp_processor_id();
u64 tb;
if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
return;
nmi_enter();
tb = get_tb();
if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
per_cpu(wd_timer_tb, cpu) = tb;
wd_smp_lock(&flags);
if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
wd_smp_unlock(&flags);
goto out;
}
set_cpu_stuck(cpu, tb);
pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu);
print_modules();
print_irqtrace_events(current);
if (regs)
show_regs(regs);
else
dump_stack();
wd_smp_unlock(&flags);
if (sysctl_hardlockup_all_cpu_backtrace)
trigger_allbutself_cpu_backtrace();
if (hardlockup_panic)
nmi_panic(regs, "Hard LOCKUP");
}
if (wd_panic_timeout_tb < 0x7fffffff)
mtspr(SPRN_DEC, wd_panic_timeout_tb);
out:
nmi_exit();
}
static void wd_timer_reset(unsigned int cpu, struct timer_list *t)
{
t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
if (wd_timer_period_ms > 1000)
t->expires = __round_jiffies_up(t->expires, cpu);
add_timer_on(t, cpu);
}
static void wd_timer_fn(unsigned long data)
{
struct timer_list *t = this_cpu_ptr(&wd_timer);
int cpu = smp_processor_id();
watchdog_timer_interrupt(cpu);
wd_timer_reset(cpu, t);
}
void arch_touch_nmi_watchdog(void)
{
int cpu = smp_processor_id();
watchdog_timer_interrupt(cpu);
}
EXPORT_SYMBOL(arch_touch_nmi_watchdog);
static void start_watchdog_timer_on(unsigned int cpu)
{
struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
per_cpu(wd_timer_tb, cpu) = get_tb();
setup_pinned_timer(t, wd_timer_fn, 0);
wd_timer_reset(cpu, t);
}
static void stop_watchdog_timer_on(unsigned int cpu)
{
struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
del_timer_sync(t);
}
static int start_wd_on_cpu(unsigned int cpu)
{
if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
WARN_ON(1);
return 0;
}
if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
return 0;
if (watchdog_suspended)
return 0;
if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
return 0;
cpumask_set_cpu(cpu, &wd_cpus_enabled);
if (cpumask_weight(&wd_cpus_enabled) == 1) {
cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
wd_smp_last_reset_tb = get_tb();
}
smp_wmb();
start_watchdog_timer_on(cpu);
return 0;
}
static int stop_wd_on_cpu(unsigned int cpu)
{
if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
return 0; /* Can happen in CPU unplug case */
stop_watchdog_timer_on(cpu);
cpumask_clear_cpu(cpu, &wd_cpus_enabled);
wd_smp_clear_cpu_pending(cpu, get_tb());
return 0;
}
static void watchdog_calc_timeouts(void)
{
wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
/* Have the SMP detector trigger a bit later */
wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
/* 2/5 is the factor that the perf based detector uses */
wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
}
void watchdog_nmi_reconfigure(void)
{
int cpu;
watchdog_calc_timeouts();
for_each_cpu(cpu, &wd_cpus_enabled)
stop_wd_on_cpu(cpu);
for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
start_wd_on_cpu(cpu);
}
/*
* This runs after lockup_detector_init() which sets up watchdog_cpumask.
*/
static int __init powerpc_watchdog_init(void)
{
int err;
watchdog_calc_timeouts();
err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
start_wd_on_cpu, stop_wd_on_cpu);
if (err < 0)
pr_warn("Watchdog could not be initialized");
return 0;
}
arch_initcall(powerpc_watchdog_init);
static void handle_backtrace_ipi(struct pt_regs *regs)
{
nmi_cpu_backtrace(regs);
}
static void raise_backtrace_ipi(cpumask_t *mask)
{
unsigned int cpu;
for_each_cpu(cpu, mask) {
if (cpu == smp_processor_id())
handle_backtrace_ipi(NULL);
else
smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
}
}
void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
{
nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
}