From: Kirill Korotaev <dev@sw.ru>
This patch adds dumping of calltraces on _all_ CPUs on AltSysRq-P and NMI
LOCKUP. It does this via sending NMI IPI interrupts to the cpus.
I saw the same patch in RedHat kernels, here goes our own version of the
patch, not sure it will be accepted, but I think it can be used by some
people at least for debugging lockups etc.
Signed-Off-By: Kirill Korotaev <dev@sw.ru>
Signed-Off-By: Pavel Emelianov <xemul@sw.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
arch/i386/kernel/nmi.c | 15 ++++++++
arch/i386/kernel/smp.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++
arch/i386/kernel/traps.c | 31 +++++++++++++----
drivers/char/sysrq.c | 5 ++
include/asm-i386/nmi.h | 2 +
include/linux/sched.h | 1
include/linux/smp.h | 6 +++
7 files changed, 137 insertions(+), 7 deletions(-)
diff -puN arch/i386/kernel/nmi.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus arch/i386/kernel/nmi.c
--- devel/arch/i386/kernel/nmi.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus 2005-08-06 15:35:04.000000000 -0700
+++ devel-akpm/arch/i386/kernel/nmi.c 2005-08-06 15:35:04.000000000 -0700
@@ -500,6 +500,21 @@ int tune_watchdog = 5*HZ;
extern void die_nmi(struct pt_regs *, const char *msg);
+static spinlock_t show_regs_lock = SPIN_LOCK_UNLOCKED;
+
+void smp_show_regs(struct pt_regs *regs, void *info)
+{
+ if (regs == NULL)
+ return;
+
+ bust_spinlocks(1);
+ spin_lock(&show_regs_lock);
+ printk("----------- IPI show regs -----------");
+ show_regs(regs);
+ spin_unlock(&show_regs_lock);
+ bust_spinlocks(0);
+}
+
void nmi_watchdog_tick (struct pt_regs * regs)
{
diff -puN arch/i386/kernel/smp.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus arch/i386/kernel/smp.c
--- devel/arch/i386/kernel/smp.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus 2005-08-06 15:35:04.000000000 -0700
+++ devel-akpm/arch/i386/kernel/smp.c 2005-08-06 15:35:04.000000000 -0700
@@ -22,6 +22,7 @@
#include <linux/cpu.h>
#include <linux/module.h>
+#include <asm/nmi.h>
#include <asm/mtrr.h>
#include <asm/tlbflush.h>
#include <mach_apic.h>
@@ -577,6 +578,89 @@ int smp_call_function (void (*func) (voi
}
EXPORT_SYMBOL(smp_call_function);
+static spinlock_t nmi_call_lock = SPIN_LOCK_UNLOCKED;
+static struct nmi_call_data_struct {
+ smp_nmi_function func;
+ void *info;
+ atomic_t started;
+ atomic_t finished;
+ cpumask_t cpus_called;
+ int wait;
+} *nmi_call_data;
+
+static int smp_nmi_callback(struct pt_regs * regs, int cpu)
+{
+ smp_nmi_function func;
+ void *info;
+ int wait;
+
+ func = nmi_call_data->func;
+ info = nmi_call_data->info;
+ wait = nmi_call_data->wait;
+ ack_APIC_irq();
+ /* prevent from calling func() multiple times */
+ if (cpu_test_and_set(cpu, nmi_call_data->cpus_called))
+ return 0;
+ /*
+ * notify initiating CPU that I've grabbed the data and am
+ * about to execute the function
+ */
+ mb();
+ atomic_inc(&nmi_call_data->started);
+ /* at this point the nmi_call_data structure is out of scope */
+ irq_enter();
+ func(regs, info);
+ irq_exit();
+ if (wait)
+ atomic_inc(&nmi_call_data->finished);
+
+ return 0;
+}
+
+/*
+ * This function tries to call func(regs, info) on each cpu.
+ * Func must be fast and non-blocking.
+ * May be called with disabled interrupts and from any context.
+ */
+int smp_nmi_call_function(smp_nmi_function func, void *info, int wait)
+{
+ struct nmi_call_data_struct data;
+ int cpus;
+
+ cpus = num_online_cpus() - 1;
+ if (!cpus)
+ return 0;
+
+ data.func = func;
+ data.info = info;
+ data.wait = wait;
+ atomic_set(&data.started, 0);
+ atomic_set(&data.finished, 0);
+ cpus_clear(data.cpus_called);
+ /* prevent this cpu from calling func if NMI happens */
+ cpu_set(smp_processor_id(), data.cpus_called);
+
+ if (!spin_trylock(&nmi_call_lock))
+ return -1;
+
+ nmi_call_data = &data;
+ set_nmi_ipi_callback(smp_nmi_callback);
+ mb();
+
+ /* Send a message to all other CPUs and wait for them to respond */
+ send_IPI_allbutself(APIC_DM_NMI);
+ while (atomic_read(&data.started) != cpus)
+ barrier();
+
+ unset_nmi_ipi_callback();
+ if (wait)
+ while (atomic_read(&data.finished) != cpus)
+ barrier();
+ spin_unlock(&nmi_call_lock);
+
+ return 0;
+}
+
static void stop_this_cpu (void * dummy)
{
/*
diff -puN arch/i386/kernel/traps.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus arch/i386/kernel/traps.c
--- devel/arch/i386/kernel/traps.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus 2005-08-06 15:35:04.000000000 -0700
+++ devel-akpm/arch/i386/kernel/traps.c 2005-08-06 15:35:04.000000000 -0700
@@ -627,6 +627,8 @@ void die_nmi (struct pt_regs *regs, cons
printk(" on CPU%d, eip %08lx, registers:\n",
smp_processor_id(), regs->eip);
show_registers(regs);
+ smp_nmi_call_function(smp_show_regs, NULL, 1);
+ bust_spinlocks(1);
printk("console shuts up ...\n");
console_silent();
spin_unlock(&nmi_print_lock);
@@ -643,6 +645,14 @@ void die_nmi (struct pt_regs *regs, cons
do_exit(SIGSEGV);
}
+static int dummy_nmi_callback(struct pt_regs * regs, int cpu)
+{
+ return 0;
+}
+
+static nmi_callback_t nmi_callback = dummy_nmi_callback;
+static nmi_callback_t nmi_ipi_callback = dummy_nmi_callback;
+
static void default_do_nmi(struct pt_regs * regs)
{
unsigned char reason = 0;
@@ -665,6 +675,9 @@ static void default_do_nmi(struct pt_reg
return;
}
#endif
+ if (nmi_ipi_callback != dummy_nmi_callback)
+ return;
+
unknown_nmi_error(reason, regs);
return;
}
@@ -681,13 +694,6 @@ static void default_do_nmi(struct pt_reg
reassert_nmi();
}
-static int dummy_nmi_callback(struct pt_regs * regs, int cpu)
-{
- return 0;
-}
-
-static nmi_callback_t nmi_callback = dummy_nmi_callback;
-
fastcall void do_nmi(struct pt_regs * regs, long error_code)
{
int cpu;
@@ -708,9 +714,20 @@ fastcall void do_nmi(struct pt_regs * re
if (!rcu_dereference(nmi_callback)(regs, cpu))
default_do_nmi(regs);
+ nmi_ipi_callback(regs, cpu);
nmi_exit();
}
+void set_nmi_ipi_callback(nmi_callback_t callback)
+{
+ nmi_ipi_callback = callback;
+}
+
+void unset_nmi_ipi_callback(void)
+{
+ nmi_ipi_callback = dummy_nmi_callback;
+}
+
void set_nmi_callback(nmi_callback_t callback)
{
rcu_assign_pointer(nmi_callback, callback);
diff -puN drivers/char/sysrq.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus drivers/char/sysrq.c
--- devel/drivers/char/sysrq.c~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus 2005-08-06 15:35:04.000000000 -0700
+++ devel-akpm/drivers/char/sysrq.c 2005-08-06 15:35:04.000000000 -0700
@@ -178,8 +178,13 @@ static struct sysrq_key_op sysrq_mountro
static void sysrq_handle_showregs(int key, struct pt_regs *pt_regs,
struct tty_struct *tty)
{
+ bust_spinlocks(1);
if (pt_regs)
show_regs(pt_regs);
+ bust_spinlocks(0);
+#ifdef __i386__
+ smp_nmi_call_function(smp_show_regs, NULL, 0);
+#endif
}
static struct sysrq_key_op sysrq_showregs_op = {
.handler = sysrq_handle_showregs,
diff -puN include/asm-i386/nmi.h~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus include/asm-i386/nmi.h
--- devel/include/asm-i386/nmi.h~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus 2005-08-06 15:35:04.000000000 -0700
+++ devel-akpm/include/asm-i386/nmi.h 2005-08-06 15:35:04.000000000 -0700
@@ -17,6 +17,7 @@ typedef int (*nmi_callback_t)(struct pt_
* set. Return 1 if the NMI was handled.
*/
void set_nmi_callback(nmi_callback_t callback);
+void set_nmi_ipi_callback(nmi_callback_t callback);
/**
* unset_nmi_callback
@@ -24,5 +25,6 @@ void set_nmi_callback(nmi_callback_t cal
* Remove the handler previously set.
*/
void unset_nmi_callback(void);
+void unset_nmi_ipi_callback(void);
#endif /* ASM_NMI_H */
diff -puN include/linux/sched.h~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus include/linux/sched.h
--- devel/include/linux/sched.h~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus 2005-08-06 15:35:04.000000000 -0700
+++ devel-akpm/include/linux/sched.h 2005-08-06 15:35:04.000000000 -0700
@@ -162,6 +162,7 @@ extern cpumask_t nohz_cpu_mask;
extern void show_state(void);
extern void show_regs(struct pt_regs *);
+extern void smp_show_regs(struct pt_regs *, void *);
/*
* TASK is a pointer to the task whose backtrace we want to see (or NULL for current
diff -puN include/linux/smp.h~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus include/linux/smp.h
--- devel/include/linux/smp.h~nmi-lockup-and-altsysrq-p-dumping-calltraces-on-_all_-cpus 2005-08-06 15:35:04.000000000 -0700
+++ devel-akpm/include/linux/smp.h 2005-08-06 15:35:04.000000000 -0700
@@ -10,6 +10,9 @@
extern void cpu_idle(void);
+struct pt_regs;
+typedef void (*smp_nmi_function)(struct pt_regs *regs, void *info);
+
#ifdef CONFIG_SMP
#include <linux/preempt.h>
@@ -56,6 +59,8 @@ extern void smp_cpus_done(unsigned int m
extern int smp_call_function (void (*func) (void *info), void *info,
int retry, int wait);
+extern int smp_nmi_call_function(smp_nmi_function func, void *info, int wait);
+
/*
* Call a function on all processors
*/
@@ -95,6 +100,7 @@ void smp_prepare_boot_cpu(void);
#define raw_smp_processor_id() 0
#define hard_smp_processor_id() 0
#define smp_call_function(func,info,retry,wait) ({ 0; })
+#define smp_nmi_call_function(func, info, wait) ({ 0; })
#define on_each_cpu(func,info,retry,wait) ({ func(info); 0; })
static inline void smp_send_reschedule(int cpu) { }
#define num_booting_cpus() 1
_