[RFC PATCH 25/30 v3] Trace irq disabled critical timings

From: Steven Rostedt
Date: Tue Jan 15 2008 - 15:52:33 EST

This patch adds latency tracing for critical timings.
In /debugfs/tracing/ three files are added:

preempt_max_latency
holds the max latency thus far (in usecs)
(default to large number so one must start latency tracing)

preempt_thresh
threshold (in usecs) to always print out if irqs off
is detected to be longer than stated here.
If irq_thresh is non-zero, then max_irq_latency
is ignored.

preempt_trace
Trace of where the latecy was detected.

preempt_fn_trace_ctrl
0 - don't use mcount
1 - use mcount to trace

Here's an example of a trace with preempt_fn_trace_ctrl == 0

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
latency: 100 us, #3/3, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
-----------------
| task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
-----------------
=> started at: _spin_lock_irqsave+0x2a/0xb7
=> ended at: _spin_unlock_irqrestore+0x32/0x5f

_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
swapper-0 1d.s3 0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
swapper-0 1d.s3 100us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
swapper-0 1d.s3 100us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)


vim:ft=help
=======


And this is a trace with irqsoff_fn_trace_ctrl == 1


=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
latency: 102 us, #12/12, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
-----------------
| task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
-----------------
=> started at: _spin_lock_irqsave+0x2a/0xb7
=> ended at: _spin_unlock_irqrestore+0x32/0x5f

_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
swapper-0 1dNs3 0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
swapper-0 1dNs3 46us : e1000_read_phy_reg+0x16/0x225 [e1000] (e1000_update_stats+0x5e2/0x64c [e1000])
swapper-0 1dNs3 46us : e1000_swfw_sync_acquire+0x10/0x99 [e1000] (e1000_read_phy_reg+0x49/0x225 [e1000])
swapper-0 1dNs3 46us : e1000_get_hw_eeprom_semaphore+0x12/0xa6 [e1000] (e1000_swfw_sync_acquire+0x36/0x99 [e1000])
swapper-0 1dNs3 47us : __const_udelay+0x9/0x47 (e1000_read_phy_reg+0x116/0x225 [e1000])
swapper-0 1dNs3 47us+: __delay+0x9/0x50 (__const_udelay+0x45/0x47)
swapper-0 1dNs3 97us : preempt_schedule+0xc/0x84 (__delay+0x4e/0x50)
swapper-0 1dNs3 98us : e1000_swfw_sync_release+0xc/0x55 [e1000] (e1000_read_phy_reg+0x211/0x225 [e1000])
swapper-0 1dNs3 99us+: e1000_put_hw_eeprom_semaphore+0x9/0x35 [e1000] (e1000_swfw_sync_release+0x50/0x55 [e1000])
swapper-0 1dNs3 101us : _spin_unlock_irqrestore+0xe/0x5f (e1000_update_stats+0x641/0x64c [e1000])
swapper-0 1dNs3 102us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
swapper-0 1dNs3 102us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)


vim:ft=help
=======


Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
arch/x86/kernel/process_64.c | 3
arch/x86/lib/thunk_64.S | 18 +
include/asm-x86/irqflags_32.h | 4
include/asm-x86/irqflags_64.h | 4
include/linux/irqflags.h | 37 ++
include/linux/mcount.h | 31 ++
kernel/fork.c | 2
kernel/lockdep.c | 25 +
lib/tracing/Kconfig | 18 +
lib/tracing/Makefile | 1
lib/tracing/trace_irqsoff.c | 558 ++++++++++++++++++++++++++++++++++++++++++
11 files changed, 680 insertions(+), 21 deletions(-)

Index: linux-compile.git/arch/x86/kernel/process_64.c
===================================================================
--- linux-compile.git.orig/arch/x86/kernel/process_64.c 2008-01-15 12:50:00.000000000 -0500
+++ linux-compile.git/arch/x86/kernel/process_64.c 2008-01-15 12:51:36.000000000 -0500
@@ -233,7 +233,10 @@ void cpu_idle (void)
*/
local_irq_disable();
enter_idle();
+ /* Don't trace irqs off for idle */
+ stop_critical_timings();
idle();
+ start_critical_timings();
/* In many cases the interrupt that ended idle
has already called exit_idle. But some idle
loops can be woken up without interrupt. */
Index: linux-compile.git/arch/x86/lib/thunk_64.S
===================================================================
--- linux-compile.git.orig/arch/x86/lib/thunk_64.S 2008-01-15 12:49:33.000000000 -0500
+++ linux-compile.git/arch/x86/lib/thunk_64.S 2008-01-15 12:51:36.000000000 -0500
@@ -47,8 +47,22 @@
thunk __up_wakeup,__up

#ifdef CONFIG_TRACE_IRQFLAGS
- thunk trace_hardirqs_on_thunk,trace_hardirqs_on
- thunk trace_hardirqs_off_thunk,trace_hardirqs_off
+ /* put return address in rdi (arg1) */
+ .macro thunk_ra name,func
+ .globl \name
+\name:
+ CFI_STARTPROC
+ SAVE_ARGS
+ /* SAVE_ARGS pushs 9 elements */
+ /* the next element would be the rip */
+ movq 9*8(%rsp), %rdi
+ call \func
+ jmp restore
+ CFI_ENDPROC
+ .endm
+
+ thunk_ra trace_hardirqs_on_thunk,trace_hardirqs_on_caller
+ thunk_ra trace_hardirqs_off_thunk,trace_hardirqs_off_caller
#endif

#ifdef CONFIG_DEBUG_LOCK_ALLOC
Index: linux-compile.git/include/asm-x86/irqflags_32.h
===================================================================
--- linux-compile.git.orig/include/asm-x86/irqflags_32.h 2008-01-15 12:49:33.000000000 -0500
+++ linux-compile.git/include/asm-x86/irqflags_32.h 2008-01-15 12:51:36.000000000 -0500
@@ -139,9 +139,9 @@ static inline int raw_irqs_disabled(void
static inline void trace_hardirqs_fixup_flags(unsigned long flags)
{
if (raw_irqs_disabled_flags(flags))
- trace_hardirqs_off();
+ __trace_hardirqs_off();
else
- trace_hardirqs_on();
+ __trace_hardirqs_on();
}

static inline void trace_hardirqs_fixup(void)
Index: linux-compile.git/include/asm-x86/irqflags_64.h
===================================================================
--- linux-compile.git.orig/include/asm-x86/irqflags_64.h 2008-01-15 12:49:33.000000000 -0500
+++ linux-compile.git/include/asm-x86/irqflags_64.h 2008-01-15 12:51:36.000000000 -0500
@@ -120,9 +120,9 @@ static inline int raw_irqs_disabled(void
static inline void trace_hardirqs_fixup_flags(unsigned long flags)
{
if (raw_irqs_disabled_flags(flags))
- trace_hardirqs_off();
+ __trace_hardirqs_off();
else
- trace_hardirqs_on();
+ __trace_hardirqs_on();
}

static inline void trace_hardirqs_fixup(void)
Index: linux-compile.git/include/linux/irqflags.h
===================================================================
--- linux-compile.git.orig/include/linux/irqflags.h 2008-01-15 12:49:33.000000000 -0500
+++ linux-compile.git/include/linux/irqflags.h 2008-01-15 12:51:36.000000000 -0500
@@ -12,10 +12,21 @@
#define _LINUX_TRACE_IRQFLAGS_H

#ifdef CONFIG_TRACE_IRQFLAGS
- extern void trace_hardirqs_on(void);
- extern void trace_hardirqs_off(void);
+# include <linux/mcount.h>
+ extern void trace_hardirqs_on_caller(unsigned long ip);
+ extern void trace_hardirqs_off_caller(unsigned long ip);
extern void trace_softirqs_on(unsigned long ip);
extern void trace_softirqs_off(unsigned long ip);
+ extern void trace_hardirqs_on(void);
+ extern void trace_hardirqs_off(void);
+ static inline void notrace __trace_hardirqs_on(void)
+ {
+ trace_hardirqs_on_caller(CALLER_ADDR0);
+ }
+ static inline void notrace __trace_hardirqs_off(void)
+ {
+ trace_hardirqs_off_caller(CALLER_ADDR0);
+ }
# define trace_hardirq_context(p) ((p)->hardirq_context)
# define trace_softirq_context(p) ((p)->softirq_context)
# define trace_hardirqs_enabled(p) ((p)->hardirqs_enabled)
@@ -28,6 +39,8 @@
#else
# define trace_hardirqs_on() do { } while (0)
# define trace_hardirqs_off() do { } while (0)
+# define __trace_hardirqs_on() do { } while (0)
+# define __trace_hardirqs_off() do { } while (0)
# define trace_softirqs_on(ip) do { } while (0)
# define trace_softirqs_off(ip) do { } while (0)
# define trace_hardirq_context(p) 0
@@ -41,24 +54,32 @@
# define INIT_TRACE_IRQFLAGS
#endif

+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+ extern void stop_critical_timings(void);
+ extern void start_critical_timings(void);
+#else
+# define stop_critical_timings() do { } while (0)
+# define start_critical_timings() do { } while (0)
+#endif
+
#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT

#include <asm/irqflags.h>

#define local_irq_enable() \
- do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
+ do { __trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
#define local_irq_disable() \
- do { raw_local_irq_disable(); trace_hardirqs_off(); } while (0)
+ do { raw_local_irq_disable(); __trace_hardirqs_off(); } while (0)
#define local_irq_save(flags) \
- do { raw_local_irq_save(flags); trace_hardirqs_off(); } while (0)
+ do { raw_local_irq_save(flags); __trace_hardirqs_off(); } while (0)

#define local_irq_restore(flags) \
do { \
if (raw_irqs_disabled_flags(flags)) { \
raw_local_irq_restore(flags); \
- trace_hardirqs_off(); \
+ __trace_hardirqs_off(); \
} else { \
- trace_hardirqs_on(); \
+ __trace_hardirqs_on(); \
raw_local_irq_restore(flags); \
} \
} while (0)
@@ -76,7 +97,7 @@
#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
#define safe_halt() \
do { \
- trace_hardirqs_on(); \
+ __trace_hardirqs_on(); \
raw_safe_halt(); \
} while (0)

Index: linux-compile.git/include/linux/mcount.h
===================================================================
--- linux-compile.git.orig/include/linux/mcount.h 2008-01-15 12:50:57.000000000 -0500
+++ linux-compile.git/include/linux/mcount.h 2008-01-15 13:12:30.000000000 -0500
@@ -6,10 +6,6 @@ extern int mcount_enabled;

#include <linux/linkage.h>

-#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
-#define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
-#define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
-
typedef void (*mcount_func_t)(unsigned long ip, unsigned long parent_ip);

struct mcount_ops {
@@ -35,4 +31,31 @@ extern void mcount(void);
# define unregister_mcount_function(ops) do { } while (0)
# define clear_mcount_function(ops) do { } while (0)
#endif /* CONFIG_MCOUNT */
+
+
+#ifdef CONFIG_FRAME_POINTER
+/* TODO: need to fix this for ARM */
+# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+# define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
+# define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
+# define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
+# define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
+# define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
+#else
+# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+# define CALLER_ADDR1 0UL
+# define CALLER_ADDR2 0UL
+# define CALLER_ADDR3 0UL
+# define CALLER_ADDR4 0UL
+# define CALLER_ADDR5 0UL
+#endif
+
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+ extern void notrace time_hardirqs_on(unsigned long a0, unsigned long a1);
+ extern void notrace time_hardirqs_off(unsigned long a0, unsigned long a1);
+#else
+# define time_hardirqs_on(a0, a1) do { } while (0)
+# define time_hardirqs_off(a0, a1) do { } while (0)
+#endif
+
#endif /* _LINUX_MCOUNT_H */
Index: linux-compile.git/kernel/fork.c
===================================================================
--- linux-compile.git.orig/kernel/fork.c 2008-01-15 12:49:33.000000000 -0500
+++ linux-compile.git/kernel/fork.c 2008-01-15 12:51:36.000000000 -0500
@@ -1010,7 +1010,7 @@ static struct task_struct *copy_process(

rt_mutex_init_task(p);

-#ifdef CONFIG_TRACE_IRQFLAGS
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_LOCKDEP)
DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
Index: linux-compile.git/kernel/lockdep.c
===================================================================
--- linux-compile.git.orig/kernel/lockdep.c 2008-01-15 12:49:33.000000000 -0500
+++ linux-compile.git/kernel/lockdep.c 2008-01-15 12:51:36.000000000 -0500
@@ -39,6 +39,7 @@
#include <linux/irqflags.h>
#include <linux/utsname.h>
#include <linux/hash.h>
+#include <linux/mcount.h>

#include <asm/sections.h>

@@ -2009,7 +2010,7 @@ void early_boot_irqs_on(void)
/*
* Hardirqs will be enabled:
*/
-void trace_hardirqs_on(void)
+void notrace trace_hardirqs_on_caller(unsigned long a0)
{
struct task_struct *curr = current;
unsigned long ip;
@@ -2050,14 +2051,27 @@ void trace_hardirqs_on(void)
curr->hardirq_enable_ip = ip;
curr->hardirq_enable_event = ++curr->irq_events;
debug_atomic_inc(&hardirqs_on_events);
+
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+ time_hardirqs_on(CALLER_ADDR0, a0);
+#endif
}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);

+void notrace trace_hardirqs_on(void) {
+ trace_hardirqs_on_caller(CALLER_ADDR0);
+}
EXPORT_SYMBOL(trace_hardirqs_on);

+void notrace trace_hardirqs_off(void) {
+ trace_hardirqs_off_caller(CALLER_ADDR0);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
/*
* Hardirqs were disabled:
*/
-void trace_hardirqs_off(void)
+void notrace trace_hardirqs_off_caller(unsigned long a0)
{
struct task_struct *curr = current;

@@ -2075,10 +2089,17 @@ void trace_hardirqs_off(void)
curr->hardirq_disable_ip = _RET_IP_;
curr->hardirq_disable_event = ++curr->irq_events;
debug_atomic_inc(&hardirqs_off_events);
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+ time_hardirqs_off(CALLER_ADDR0, a0);
+#endif
} else
debug_atomic_inc(&redundant_hardirqs_off);
}

+void notrace trace_hardirqs_off(void) {
+ trace_hardirqs_off_caller(CALLER_ADDR0);
+}
+
EXPORT_SYMBOL(trace_hardirqs_off);

/*
Index: linux-compile.git/lib/tracing/Kconfig
===================================================================
--- linux-compile.git.orig/lib/tracing/Kconfig 2008-01-15 12:51:21.000000000 -0500
+++ linux-compile.git/lib/tracing/Kconfig 2008-01-15 13:12:36.000000000 -0500
@@ -24,3 +24,21 @@ config FUNCTION_TRACER
insert a call to an architecture specific __mcount routine,
that the debugging mechanism using this facility will hook by
providing a set of inline routines.
+
+config CRITICAL_IRQSOFF_TIMING
+ bool "Interrupts-off critical section latency timing"
+ default n
+ depends on TRACE_IRQFLAGS_SUPPORT
+ depends on GENERIC_TIME
+ select TRACE_IRQFLAGS
+ select TRACING
+ help
+ This option measures the time spent in irqs-off critical
+ sections, with microsecond accuracy.
+
+ The default measurement method is a maximum search, which is
+ disabled by default and can be runtime (re-)started
+ via:
+
+ echo 0 > /debug/tracing/preempt_max_latency
+
Index: linux-compile.git/lib/tracing/Makefile
===================================================================
--- linux-compile.git.orig/lib/tracing/Makefile 2008-01-15 12:51:21.000000000 -0500
+++ linux-compile.git/lib/tracing/Makefile 2008-01-15 13:12:36.000000000 -0500
@@ -2,5 +2,6 @@ obj-$(CONFIG_MCOUNT) += libmcount.o

obj-$(CONFIG_TRACING) += tracer.o
obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
+obj-$(CONFIG_CRITICAL_IRQSOFF_TIMING) += trace_irqsoff.o

libmcount-y := mcount.o
Index: linux-compile.git/lib/tracing/trace_irqsoff.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-compile.git/lib/tracing/trace_irqsoff.c 2008-01-15 13:13:07.000000000 -0500
@@ -0,0 +1,558 @@
+/*
+ * trace irqs off criticall timings
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@xxxxxxxxxx>
+ *
+ * From code in the latency_tracer, that is:
+ *
+ * Copyright (C) 2004-2006 Ingo Molnar
+ * Copyright (C) 2004 William Lee Irwin III
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace irqsoff_trace __read_mostly;
+static struct tracing_trace max_tr __read_mostly;
+static DEFINE_PER_CPU(struct tracing_trace_cpu, irqsoff_trace_cpu);
+static DEFINE_PER_CPU(struct tracing_trace_cpu, max_data);
+static unsigned long preempt_max_latency = (cycle_t)ULONG_MAX;
+static unsigned long preempt_thresh;
+static __cacheline_aligned_in_smp DEFINE_MUTEX(max_mutex);
+static int trace_enabled __read_mostly;
+
+/*
+ * max trace is switched with this buffer.
+ */
+static void *max_buffer;
+
+/*
+ * Sequence count - we record it when starting a measurement and
+ * skip the latency if the sequence has changed - some other section
+ * did a maximum and could disturb our measurement with serial console
+ * printouts, etc. Truly coinciding maximum latencies should be rare
+ * and what happens together happens separately as well, so this doesnt
+ * decrease the validity of the maximum found:
+ */
+static __cacheline_aligned_in_smp unsigned long max_sequence;
+
+/*
+ * Should this new latency be reported/recorded?
+ */
+static int notrace report_latency(cycle_t delta)
+{
+ if (preempt_thresh) {
+ if (delta < preempt_thresh)
+ return 0;
+ } else {
+ if (delta <= preempt_max_latency)
+ return 0;
+ }
+ return 1;
+}
+
+/*
+ * Copy the new maximum trace into the separate maximum-trace
+ * structure. (this way the maximum trace is permanently saved,
+ * for later retrieval via /proc/latency_trace)
+ */
+static void update_max_tr(struct tracing_trace *tr,
+ struct tracing_trace_cpu *data,
+ int cpu)
+{
+ struct tracing_trace_cpu *save;
+ int i;
+
+#ifdef CONFIG_PREEMPT
+ WARN_ON(!preempt_count() && !irqs_disabled());
+#endif
+
+ max_tr.cpu = cpu;
+ save = max_tr.data[cpu];
+
+ /* clear out all the previous traces */
+ for_each_possible_cpu(i) {
+ if (max_tr.data[i]->trace)
+ max_tr.data[i]->trace = NULL;
+ }
+
+ max_tr.time_start = data->preempt_timestamp;
+
+ memcpy(save, data, sizeof(*data));
+ save->saved_latency = preempt_max_latency;
+
+ memcpy(save->comm, current->comm, TASK_COMM_LEN);
+ save->pid = current->pid;
+ save->uid = current->uid;
+ save->nice = current->static_prio - 20 - MAX_RT_PRIO;
+ save->policy = current->policy;
+ save->rt_priority = current->rt_priority;
+
+ /* from memcpy above: save->trace = data->trace */
+ data->trace = max_buffer;
+ max_buffer = save->trace;
+}
+
+cycle_t notrace usecs_to_cycles(unsigned long usecs);
+
+static void notrace
+check_critical_timing(struct tracing_trace *tr,
+ struct tracing_trace_cpu *data,
+ unsigned long parent_ip,
+ int cpu)
+{
+ unsigned long latency, t0, t1;
+ cycle_t T0, T1, T2, delta;
+ unsigned long flags;
+
+ /*
+ * usecs conversion is slow so we try to delay the conversion
+ * as long as possible:
+ */
+ T0 = data->preempt_timestamp;
+ T1 = now();
+ delta = T1-T0;
+
+ local_save_flags(flags);
+
+ if (!report_latency(delta))
+ goto out;
+
+ tracing_function_trace(tr, data, CALLER_ADDR0, parent_ip, flags);
+ /*
+ * Update the timestamp, because the trace entry above
+ * might change it (it can only get larger so the latency
+ * is fair to be reported):
+ */
+ T2 = now();
+
+ delta = T2-T0;
+
+ latency = cycles_to_usecs(delta);
+
+ if (data->critical_sequence != max_sequence ||
+ !mutex_trylock(&max_mutex))
+ goto out;
+
+ preempt_max_latency = delta;
+ t0 = cycles_to_usecs(T0);
+ t1 = cycles_to_usecs(T1);
+
+ data->critical_end = parent_ip;
+
+ update_max_tr(tr, data, cpu);
+
+ if (preempt_thresh)
+ printk(KERN_INFO "(%16s-%-5d|#%d): %lu us critical section "
+ "violates %lu us threshold.\n"
+ " => started at timestamp %lu: ",
+ current->comm, current->pid,
+ raw_smp_processor_id(),
+ latency, cycles_to_usecs(preempt_thresh), t0);
+ else
+ printk(KERN_INFO "(%16s-%-5d|#%d): new %lu us maximum-latency "
+ "critical section.\n => started at timestamp %lu: ",
+ current->comm, current->pid,
+ raw_smp_processor_id(),
+ latency, t0);
+
+ print_symbol(KERN_CONT "<%s>\n", data->critical_start);
+ printk(KERN_CONT " => ended at timestamp %lu: ", t1);
+ print_symbol(KERN_CONT "<%s>\n", data->critical_end);
+ dump_stack();
+ t1 = cycles_to_usecs(now());
+ printk(KERN_CONT " => dump-end timestamp %lu\n\n", t1);
+
+ max_sequence++;
+
+ mutex_unlock(&max_mutex);
+
+out:
+ data->critical_sequence = max_sequence;
+ data->preempt_timestamp = now();
+ tracing_reset(data);
+ tracing_function_trace(tr, data, CALLER_ADDR0, parent_ip, flags);
+}
+
+static inline void notrace
+start_critical_timing(unsigned long ip, unsigned long parent_ip)
+{
+ int cpu = raw_smp_processor_id();
+ struct tracing_trace *tr = &irqsoff_trace;
+ struct tracing_trace_cpu *data = tr->data[cpu];
+ unsigned long flags;
+
+ if (unlikely(!data) || unlikely(!data->trace) ||
+ data->critical_start || atomic_read(&data->disabled))
+ return;
+
+ atomic_inc(&data->disabled);
+
+ data->critical_sequence = max_sequence;
+ data->preempt_timestamp = now();
+ data->critical_start = parent_ip;
+ tracing_reset(data);
+
+ local_save_flags(flags);
+ tracing_function_trace(tr, data, ip, parent_ip, flags);
+
+ atomic_dec(&data->disabled);
+}
+
+static inline void notrace
+stop_critical_timing(unsigned long ip, unsigned long parent_ip)
+{
+ int cpu = raw_smp_processor_id();
+ struct tracing_trace *tr = &irqsoff_trace;
+ struct tracing_trace_cpu *data = tr->data[cpu];
+ unsigned long flags;
+
+ if (unlikely(!data) || unlikely(!data->trace) ||
+ !data->critical_start || atomic_read(&data->disabled))
+ return;
+
+ atomic_inc(&data->disabled);
+ local_save_flags(flags);
+ tracing_function_trace(tr, data, ip, parent_ip, flags);
+ check_critical_timing(tr, data, parent_ip, cpu);
+ data->critical_start = 0;
+ atomic_dec(&data->disabled);
+}
+
+void notrace start_critical_timings(void)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ start_critical_timing(CALLER_ADDR0, 0);
+}
+
+void notrace stop_critical_timings(void)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ stop_critical_timing(CALLER_ADDR0, 0);
+}
+
+#ifdef CONFIG_LOCKDEP
+void notrace time_hardirqs_on(unsigned long a0, unsigned long a1)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ stop_critical_timing(a0, a1);
+}
+
+void notrace time_hardirqs_off(unsigned long a0, unsigned long a1)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ start_critical_timing(a0, a1);
+}
+
+#else /* !CONFIG_LOCKDEP */
+
+/*
+ * Stubs:
+ */
+
+void early_boot_irqs_off(void)
+{
+}
+
+void early_boot_irqs_on(void)
+{
+}
+
+void trace_softirqs_on(unsigned long ip)
+{
+}
+
+void trace_softirqs_off(unsigned long ip)
+{
+}
+
+inline void print_irqtrace_events(struct task_struct *curr)
+{
+}
+
+/*
+ * We are only interested in hardirq on/off events:
+ */
+void notrace trace_hardirqs_on(void)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ stop_critical_timing(CALLER_ADDR0, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+void notrace trace_hardirqs_off(void)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ start_critical_timing(CALLER_ADDR0, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
+void notrace trace_hardirqs_on_caller(unsigned long caller_addr)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ stop_critical_timing(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
+
+void notrace trace_hardirqs_off_caller(unsigned long caller_addr)
+{
+ unsigned long flags;
+
+ local_save_flags(flags);
+
+ if (irqs_disabled_flags(flags))
+ start_critical_timing(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_off_caller);
+
+#endif /* CONFIG_LOCKDEP */
+
+
+#ifdef CONFIG_MCOUNT
+static void notrace irqsoff_trace_call(unsigned long ip,
+ unsigned long parent_ip)
+{
+ struct tracing_trace *tr = &irqsoff_trace;
+ struct tracing_trace_cpu *data;
+ unsigned long flags;
+ int cpu;
+
+ if (unlikely(!trace_enabled))
+ return;
+
+ local_save_flags(flags);
+
+ if (!irqs_disabled_flags(flags))
+ return;
+
+ cpu = raw_smp_processor_id();
+ data = tr->data[cpu];
+ atomic_inc(&data->disabled);
+
+ if (likely(atomic_read(&data->disabled) == 1))
+ tracing_function_trace(tr, data, ip, parent_ip, flags);
+
+ atomic_dec(&data->disabled);
+}
+
+static struct mcount_ops trace_ops __read_mostly =
+{
+ .func = irqsoff_trace_call,
+};
+#endif /* CONFIG_MCOUNT */
+
+#ifdef CONFIG_DEBUG_FS
+static void irqsoff_start(struct tracing_iterator *iter)
+{
+ mutex_lock(&max_mutex);
+}
+
+static void irqsoff_stop(struct tracing_iterator *iter)
+{
+ mutex_unlock(&max_mutex);
+}
+
+static ssize_t max_irq_lat_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ unsigned long *ptr = filp->private_data;
+ char buf[64];
+ int r;
+
+ r = snprintf(buf, 64, "%ld\n", *ptr == -1 ? : cycles_to_usecs(*ptr));
+ if (r > 64)
+ r = 64;
+ return simple_read_from_buffer(ubuf, cnt, ppos,
+ buf, r);
+}
+static ssize_t max_irq_lat_write(struct file *filp,
+ const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ long *ptr = filp->private_data;
+ long val;
+ char buf[64];
+
+ if (cnt > 63)
+ cnt = 63;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = 0;
+
+ val = simple_strtoul(buf, NULL, 10);
+
+ *ptr = usecs_to_cycles(val);
+
+ return cnt;
+}
+
+static struct file_operations max_irq_lat_fops = {
+ .open = tracing_open_generic,
+ .read = max_irq_lat_read,
+ .write = max_irq_lat_write,
+};
+
+static void irqsoff_trace_ctrl_update(struct tracing_trace *tr,
+ unsigned long val)
+{
+ val = !!val;
+
+ if (tr->ctrl ^ val) {
+ if (val) {
+ trace_enabled = 1;
+ register_mcount_function(&trace_ops);
+ } else {
+ trace_enabled = 0;
+ unregister_mcount_function(&trace_ops);
+ }
+ tr->ctrl = val;
+ }
+}
+
+static __init void irqsoff_trace_init_debugfs(void)
+{
+ struct dentry *d_tracer;
+ struct dentry *entry;
+
+ d_tracer = tracing_init_dentry();
+
+ irqsoff_trace.ctrl_update = irqsoff_trace_ctrl_update;
+
+#ifdef CONFIG_MCOUNT
+ entry = debugfs_create_file("preempt_fn_trace_ctrl", 0644, d_tracer,
+ &irqsoff_trace, &tracing_ctrl_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs"
+ " 'preempt_fn_trace' entry\n");
+#endif
+
+ entry = debugfs_create_file("preempt_max_latency", 0644, d_tracer,
+ &preempt_max_latency, &max_irq_lat_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs 'ctrl' entry\n");
+
+ entry = debugfs_create_file("preempt_thresh", 0644, d_tracer,
+ &preempt_thresh, &max_irq_lat_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs 'ctrl' entry\n");
+
+ entry = debugfs_create_file("preempt_trace", 0444, d_tracer,
+ &max_tr, &tracing_lt_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs 'irqsoff_trace' entry\n");
+}
+
+#endif /* CONFIG_DEBUGFS */
+
+static void notrace irqsoff_trace_open(struct tracing_iterator *iter)
+{
+ /* stop the trace while dumping */
+ if (iter->tr->ctrl)
+ trace_enabled = 0;
+}
+
+static void notrace irqsoff_trace_close(struct tracing_iterator *iter)
+{
+ if (iter->tr->ctrl)
+ trace_enabled = 1;
+}
+
+__init static int trace_irqsoff_alloc_buffers(void)
+{
+ const int order = page_order(TRACING_NR_ENTRIES * TRACING_ENTRY_SIZE);
+ const unsigned long size = (1UL << order) << PAGE_SHIFT;
+ struct tracing_entry *array;
+ int i;
+
+ for_each_possible_cpu(i) {
+ irqsoff_trace.data[i] = &per_cpu(irqsoff_trace_cpu, i);
+ max_tr.data[i] = &per_cpu(max_data, i);
+
+ array = (struct tracing_entry *)
+ __get_free_pages(GFP_KERNEL, order);
+ if (array == NULL) {
+ printk(KERN_ERR "irqsoff tracer: failed to allocate"
+ " %ld bytes for trace buffer!\n", size);
+ goto free_buffers;
+ }
+ irqsoff_trace.data[i]->trace = array;
+ }
+
+ array = (struct tracing_entry *)
+ __get_free_pages(GFP_KERNEL, order);
+ if (array == NULL) {
+ printk(KERN_ERR "irqsoff tracer: failed to allocate"
+ " %ld bytes for trace buffer!\n", size);
+ goto free_buffers;
+ }
+ max_buffer = array;
+
+ /*
+ * Since we allocate by orders of pages, we may be able to
+ * round up a bit.
+ */
+ irqsoff_trace.entries = size / TRACING_ENTRY_SIZE;
+ max_tr.entries = irqsoff_trace.entries;
+ max_tr.start = irqsoff_start;
+ max_tr.stop = irqsoff_stop;
+
+ pr_info("irqs off tracer: %ld bytes allocated for %ld",
+ size, TRACING_NR_ENTRIES);
+ pr_info(" entries of %d bytes\n", (int)TRACING_ENTRY_SIZE);
+ pr_info(" actual entries %ld\n", irqsoff_trace.entries);
+
+ irqsoff_trace_init_debugfs();
+
+ irqsoff_trace.open = irqsoff_trace_open;
+ irqsoff_trace.close = irqsoff_trace_close;
+
+ return 0;
+
+ free_buffers:
+ for (i-- ; i >= 0; i--) {
+ struct tracing_trace_cpu *data = irqsoff_trace.data[i];
+
+ if (data && data->trace) {
+ free_pages((unsigned long)data->trace, order);
+ data->trace = NULL;
+ }
+ }
+ return -ENOMEM;
+}
+
+device_initcall(trace_irqsoff_alloc_buffers);

--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/