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Message-ID: <20081103180328.GA20434@elte.hu>
Date: Mon, 3 Nov 2008 19:03:29 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Steven Rostedt <rostedt@...dmis.org>
Subject: [git pull] tracing fixes
Linus,
Please pull the latest tracing-fixes-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git tracing-fixes-for-linus
Thanks,
Ingo
------------------>
Al Viro (1):
tracing, alpha: undefined reference to `save_stack_trace'
Steven Rostedt (2):
ftrace: use kretprobe trampoline name to test in output
tracing, ring-buffer: add paranoid checks for loops
kernel/trace/Kconfig | 2 +-
kernel/trace/ring_buffer.c | 56 ++++++++++++++++++++++++++++++++++++++++++++
kernel/trace/trace.c | 41 ++++++++++++++++++--------------
3 files changed, 80 insertions(+), 19 deletions(-)
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index b58f43b..33dbefd 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -25,7 +25,7 @@ config TRACING
bool
select DEBUG_FS
select RING_BUFFER
- select STACKTRACE
+ select STACKTRACE if STACKTRACE_SUPPORT
select TRACEPOINTS
select NOP_TRACER
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index cedf4e2..3f33806 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1022,8 +1022,23 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event;
u64 ts, delta;
int commit = 0;
+ int nr_loops = 0;
again:
+ /*
+ * We allow for interrupts to reenter here and do a trace.
+ * If one does, it will cause this original code to loop
+ * back here. Even with heavy interrupts happening, this
+ * should only happen a few times in a row. If this happens
+ * 1000 times in a row, there must be either an interrupt
+ * storm or we have something buggy.
+ * Bail!
+ */
+ if (unlikely(++nr_loops > 1000)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ return NULL;
+ }
+
ts = ring_buffer_time_stamp(cpu_buffer->cpu);
/*
@@ -1532,10 +1547,23 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *reader = NULL;
unsigned long flags;
+ int nr_loops = 0;
spin_lock_irqsave(&cpu_buffer->lock, flags);
again:
+ /*
+ * This should normally only loop twice. But because the
+ * start of the reader inserts an empty page, it causes
+ * a case where we will loop three times. There should be no
+ * reason to loop four times (that I know of).
+ */
+ if (unlikely(++nr_loops > 3)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ reader = NULL;
+ goto out;
+ }
+
reader = cpu_buffer->reader_page;
/* If there's more to read, return this page */
@@ -1665,6 +1693,7 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
struct buffer_page *reader;
+ int nr_loops = 0;
if (!cpu_isset(cpu, buffer->cpumask))
return NULL;
@@ -1672,6 +1701,19 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
cpu_buffer = buffer->buffers[cpu];
again:
+ /*
+ * We repeat when a timestamp is encountered. It is possible
+ * to get multiple timestamps from an interrupt entering just
+ * as one timestamp is about to be written. The max times
+ * that this can happen is the number of nested interrupts we
+ * can have. Nesting 10 deep of interrupts is clearly
+ * an anomaly.
+ */
+ if (unlikely(++nr_loops > 10)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ return NULL;
+ }
+
reader = rb_get_reader_page(cpu_buffer);
if (!reader)
return NULL;
@@ -1722,6 +1764,7 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
struct ring_buffer *buffer;
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
+ int nr_loops = 0;
if (ring_buffer_iter_empty(iter))
return NULL;
@@ -1730,6 +1773,19 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
buffer = cpu_buffer->buffer;
again:
+ /*
+ * We repeat when a timestamp is encountered. It is possible
+ * to get multiple timestamps from an interrupt entering just
+ * as one timestamp is about to be written. The max times
+ * that this can happen is the number of nested interrupts we
+ * can have. Nesting 10 deep of interrupts is clearly
+ * an anomaly.
+ */
+ if (unlikely(++nr_loops > 10)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ return NULL;
+ }
+
if (rb_per_cpu_empty(cpu_buffer))
return NULL;
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8a499e2..9f3b478 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -705,6 +705,7 @@ static void ftrace_trace_stack(struct trace_array *tr,
unsigned long flags,
int skip, int pc)
{
+#ifdef CONFIG_STACKTRACE
struct ring_buffer_event *event;
struct stack_entry *entry;
struct stack_trace trace;
@@ -730,6 +731,7 @@ static void ftrace_trace_stack(struct trace_array *tr,
save_stack_trace(&trace);
ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
+#endif
}
void __trace_stack(struct trace_array *tr,
@@ -1086,17 +1088,20 @@ static void s_stop(struct seq_file *m, void *p)
mutex_unlock(&trace_types_lock);
}
-#define KRETPROBE_MSG "[unknown/kretprobe'd]"
-
#ifdef CONFIG_KRETPROBES
-static inline int kretprobed(unsigned long addr)
+static inline const char *kretprobed(const char *name)
{
- return addr == (unsigned long)kretprobe_trampoline;
+ static const char tramp_name[] = "kretprobe_trampoline";
+ int size = sizeof(tramp_name);
+
+ if (strncmp(tramp_name, name, size) == 0)
+ return "[unknown/kretprobe'd]";
+ return name;
}
#else
-static inline int kretprobed(unsigned long addr)
+static inline const char *kretprobed(const char *name)
{
- return 0;
+ return name;
}
#endif /* CONFIG_KRETPROBES */
@@ -1105,10 +1110,13 @@ seq_print_sym_short(struct trace_seq *s, const char *fmt, unsigned long address)
{
#ifdef CONFIG_KALLSYMS
char str[KSYM_SYMBOL_LEN];
+ const char *name;
kallsyms_lookup(address, NULL, NULL, NULL, str);
- return trace_seq_printf(s, fmt, str);
+ name = kretprobed(str);
+
+ return trace_seq_printf(s, fmt, name);
#endif
return 1;
}
@@ -1119,9 +1127,12 @@ seq_print_sym_offset(struct trace_seq *s, const char *fmt,
{
#ifdef CONFIG_KALLSYMS
char str[KSYM_SYMBOL_LEN];
+ const char *name;
sprint_symbol(str, address);
- return trace_seq_printf(s, fmt, str);
+ name = kretprobed(str);
+
+ return trace_seq_printf(s, fmt, name);
#endif
return 1;
}
@@ -1375,10 +1386,7 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
seq_print_ip_sym(s, field->ip, sym_flags);
trace_seq_puts(s, " (");
- if (kretprobed(field->parent_ip))
- trace_seq_puts(s, KRETPROBE_MSG);
- else
- seq_print_ip_sym(s, field->parent_ip, sym_flags);
+ seq_print_ip_sym(s, field->parent_ip, sym_flags);
trace_seq_puts(s, ")\n");
break;
}
@@ -1494,12 +1502,9 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
ret = trace_seq_printf(s, " <-");
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
- if (kretprobed(field->parent_ip))
- ret = trace_seq_puts(s, KRETPROBE_MSG);
- else
- ret = seq_print_ip_sym(s,
- field->parent_ip,
- sym_flags);
+ ret = seq_print_ip_sym(s,
+ field->parent_ip,
+ sym_flags);
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
}
--
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