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Date: Fri, 31 Jul 2009 14:56:57 -0400 (EDT)
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>,
linux-rt-users <linux-rt-users@...r.kernel.org>
cc: Thomas Gleixner <tglx@...utronix.de>,
Clark Williams <clark.williams@...il.com>,
Darren Hart <dvhltc@...ibm.com>
Subject: Re: [PATCH][RT] stacktrace: dump out last preempt disable
locations
Updated patch, silly quilt, I forgot to add a fill. I've been spoiled with
git.
-- Steve
On Thu, 30 Jul 2009, Steven Rostedt wrote:
> Thomas,
>
> This patch was somehow dropped from the 31-rt port. It is very useful
> since it shows the last locations that preemption was disabled. The bugs
> that Darren and Clark are seeing would probably be spotted by this patch.
> Could you add it back.
>
> Ingo wrote the original version of this code, but as things changed I
> needed to rewrite it.
>
> -- Steve
>
Track preempt disable nesting
This code was largly influenced by work from Ingo Molnar.
Signed-off-by: Steven Rostedt <srostedt@...hat.com>
---
arch/arm/kernel/traps.c | 1 +
arch/x86/kernel/dumpstack.c | 1 +
include/linux/preempt.h | 3 ++-
include/linux/sched.h | 11 +++++++++++
kernel/sched.c | 17 +++++++++++++++--
kernel/trace/Kconfig | 8 ++++++++
kernel/trace/Makefile | 2 ++
kernel/trace/preempt-trace.c | 30 ++++++++++++++++++++++++++++++
8 files changed, 70 insertions(+), 3 deletions(-)
Index: linux-tip.git/arch/arm/kernel/traps.c
===================================================================
--- linux-tip.git.orig/arch/arm/kernel/traps.c 2009-07-31 14:49:38.000000000 -0400
+++ linux-tip.git/arch/arm/kernel/traps.c 2009-07-31 14:51:12.000000000 -0400
@@ -365,6 +365,7 @@ asmlinkage void do_unexp_fiq (struct pt_
{
printk("Hmm. Unexpected FIQ received, but trying to continue\n");
printk("You may have a hardware problem...\n");
+ print_preempt_trace(current);
}
/*
Index: linux-tip.git/include/linux/preempt.h
===================================================================
--- linux-tip.git.orig/include/linux/preempt.h 2009-07-31 14:49:38.000000000 -0400
+++ linux-tip.git/include/linux/preempt.h 2009-07-31 14:51:12.000000000 -0400
@@ -10,7 +10,8 @@
#include <linux/linkage.h>
#include <linux/list.h>
-#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) || \
+ defined(CONFIG_PREEMPT_TRACE)
extern void add_preempt_count(int val);
extern void sub_preempt_count(int val);
#else
Index: linux-tip.git/include/linux/sched.h
===================================================================
--- linux-tip.git.orig/include/linux/sched.h 2009-07-31 14:49:38.000000000 -0400
+++ linux-tip.git/include/linux/sched.h 2009-07-31 14:51:12.000000000 -0400
@@ -1437,6 +1437,11 @@ struct task_struct {
#define MAX_PREEMPT_TRACE 25
#define MAX_LOCK_STACK MAX_PREEMPT_TRACE
+#ifdef CONFIG_PREEMPT_TRACE
+ unsigned long preempt_trace_eip[MAX_PREEMPT_TRACE];
+ unsigned long preempt_trace_parent_eip[MAX_PREEMPT_TRACE];
+#endif
+
#ifdef CONFIG_DEBUG_PREEMPT
atomic_t lock_count;
# ifdef CONFIG_PREEMPT_RT
@@ -2605,6 +2610,12 @@ static inline int task_is_current(struct
}
#endif
+#ifdef CONFIG_PREEMPT_TRACE
+void print_preempt_trace(struct task_struct *tsk);
+#else
+static inline void print_preempt_trace(struct task_struct *tsk) { }
+#endif
+
#endif /* __KERNEL__ */
#endif
Index: linux-tip.git/kernel/sched.c
===================================================================
--- linux-tip.git.orig/kernel/sched.c 2009-07-31 14:49:38.000000000 -0400
+++ linux-tip.git/kernel/sched.c 2009-07-31 14:51:12.000000000 -0400
@@ -5349,10 +5349,14 @@ EXPORT_SYMBOL(preempt_enable_no_resched)
#endif
#if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
- defined(CONFIG_PREEMPT_TRACER))
+ defined(CONFIG_PREEMPT_TRACER) || \
+ defined(CONFIG_PREEMPT_TRACE))
void __kprobes add_preempt_count(int val)
{
+ unsigned long eip = CALLER_ADDR0;
+ unsigned long parent_eip = get_parent_ip(CALLER_ADDR1);
+
#ifdef CONFIG_DEBUG_PREEMPT
/*
* Underflow?
@@ -5361,6 +5365,15 @@ void __kprobes add_preempt_count(int val
return;
#endif
preempt_count() += val;
+#ifdef CONFIG_PREEMPT_TRACE
+ if (val <= 10) {
+ unsigned int idx = preempt_count() & PREEMPT_MASK;
+ if (idx < MAX_PREEMPT_TRACE) {
+ current->preempt_trace_eip[idx] = eip;
+ current->preempt_trace_parent_eip[idx] = parent_eip;
+ }
+ }
+#endif
#ifdef CONFIG_DEBUG_PREEMPT
/*
* Spinlock count overflowing soon?
@@ -5369,7 +5382,7 @@ void __kprobes add_preempt_count(int val
PREEMPT_MASK - 10);
#endif
if (preempt_count() == val)
- trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+ trace_preempt_off(eip, parent_eip);
}
EXPORT_SYMBOL(add_preempt_count);
Index: linux-tip.git/kernel/trace/Kconfig
===================================================================
--- linux-tip.git.orig/kernel/trace/Kconfig 2009-07-31 14:49:38.000000000 -0400
+++ linux-tip.git/kernel/trace/Kconfig 2009-07-31 14:51:12.000000000 -0400
@@ -502,6 +502,14 @@ config RING_BUFFER_BENCHMARK
If unsure, say N
+config PREEMPT_TRACE
+ bool "Keep a record of preempt disabled spots"
+ depends on DEBUG_KERNEL
+ depends on PREEMPT
+ select TRACING
+ help
+ Keeps a record of the last 25 preempt disabled locations.
+
endif # FTRACE
endif # TRACING_SUPPORT
Index: linux-tip.git/kernel/trace/Makefile
===================================================================
--- linux-tip.git.orig/kernel/trace/Makefile 2009-07-31 14:49:38.000000000 -0400
+++ linux-tip.git/kernel/trace/Makefile 2009-07-31 14:51:12.000000000 -0400
@@ -55,4 +55,6 @@ obj-$(CONFIG_FTRACE_SYSCALLS) += trace_s
obj-$(CONFIG_EVENT_PROFILE) += trace_event_profile.o
obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
+obj-$(CONFIG_PREEMPT_TRACE) += preempt-trace.o
+
libftrace-y := ftrace.o
Index: linux-tip.git/kernel/trace/preempt-trace.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-tip.git/kernel/trace/preempt-trace.c 2009-07-31 14:51:12.000000000 -0400
@@ -0,0 +1,30 @@
+#include <linux/sched.h>
+#include <linux/hardirq.h>
+#include <linux/kallsyms.h>
+
+void print_preempt_trace(struct task_struct *task)
+{
+ unsigned int count;
+ unsigned int i, lim;
+
+ if (!task)
+ task = current;
+
+ count = task_thread_info(task)->preempt_count;
+ lim = count & PREEMPT_MASK;
+
+ if (lim >= MAX_PREEMPT_TRACE)
+ lim = MAX_PREEMPT_TRACE-1;
+ printk("---------------------------\n");
+ printk("| preempt count: %08x ]\n", count);
+ printk("| %d-level deep critical section nesting:\n", lim);
+ printk("----------------------------------------\n");
+ for (i = 1; i <= lim; i++) {
+ printk(".. [<%08lx>] .... ", task->preempt_trace_eip[i]);
+ print_symbol("%s\n", task->preempt_trace_eip[i]);
+ printk(".....[<%08lx>] .. ( <= ",
+ task->preempt_trace_parent_eip[i]);
+ print_symbol("%s)\n", task->preempt_trace_parent_eip[i]);
+ }
+ printk("\n");
+}
Index: linux-tip.git/arch/x86/kernel/dumpstack.c
===================================================================
--- linux-tip.git.orig/arch/x86/kernel/dumpstack.c 2009-07-31 14:49:38.000000000 -0400
+++ linux-tip.git/arch/x86/kernel/dumpstack.c 2009-07-31 14:51:12.000000000 -0400
@@ -154,6 +154,7 @@ show_trace_log_lvl(struct task_struct *t
{
printk("%sCall Trace:\n", log_lvl);
dump_trace(task, regs, stack, bp, &print_trace_ops, log_lvl);
+ print_preempt_trace(task);
}
void show_trace(struct task_struct *task, struct pt_regs *regs,
--
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