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Date: Sun, 31 Jan 2010 18:23:37 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
Frédéric Weisbecker
<fweisbec@...il.com>, Andrew Morton <akpm@...ux-foundation.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
------------------>
Mike Frysinger (1):
tracing/documentation: Cover new frame pointer semantics
Steven Rostedt (3):
tracing: Prevent kernel oops with corrupted buffer
ring-buffer: Check if ring buffer iterator has stale data
ring-buffer: Check for end of page in iterator
Yang Hongyang (1):
tracing/documentation: Fix a typo in ftrace.txt
Documentation/trace/ftrace-design.txt | 26 +++++++++++++++++++++++---
Documentation/trace/ftrace.txt | 2 +-
kernel/trace/Kconfig | 4 +---
kernel/trace/ring_buffer.c | 24 +++++++++++++++++++++---
kernel/trace/trace.c | 5 +++++
5 files changed, 51 insertions(+), 10 deletions(-)
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index 239f14b..6a5a579 100644
--- a/Documentation/trace/ftrace-design.txt
+++ b/Documentation/trace/ftrace-design.txt
@@ -1,5 +1,6 @@
function tracer guts
====================
+ By Mike Frysinger
Introduction
------------
@@ -173,14 +174,16 @@ void ftrace_graph_caller(void)
unsigned long *frompc = &...;
unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
- prepare_ftrace_return(frompc, selfpc);
+ /* passing frame pointer up is optional -- see below */
+ prepare_ftrace_return(frompc, selfpc, frame_pointer);
/* restore all state needed by the ABI */
}
#endif
-For information on how to implement prepare_ftrace_return(), simply look at
-the x86 version. The only architecture-specific piece in it is the setup of
+For information on how to implement prepare_ftrace_return(), simply look at the
+x86 version (the frame pointer passing is optional; see the next section for
+more information). The only architecture-specific piece in it is the setup of
the fault recovery table (the asm(...) code). The rest should be the same
across architectures.
@@ -205,6 +208,23 @@ void return_to_handler(void)
#endif
+HAVE_FUNCTION_GRAPH_FP_TEST
+---------------------------
+
+An arch may pass in a unique value (frame pointer) to both the entering and
+exiting of a function. On exit, the value is compared and if it does not
+match, then it will panic the kernel. This is largely a sanity check for bad
+code generation with gcc. If gcc for your port sanely updates the frame
+pointer under different opitmization levels, then ignore this option.
+
+However, adding support for it isn't terribly difficult. In your assembly code
+that calls prepare_ftrace_return(), pass the frame pointer as the 3rd argument.
+Then in the C version of that function, do what the x86 port does and pass it
+along to ftrace_push_return_trace() instead of a stub value of 0.
+
+Similarly, when you call ftrace_return_to_handler(), pass it the frame pointer.
+
+
HAVE_FTRACE_NMI_ENTER
---------------------
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 8179692..bab3040 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1625,7 +1625,7 @@ If I am only interested in sys_nanosleep and hrtimer_interrupt:
# echo sys_nanosleep hrtimer_interrupt \
> set_ftrace_filter
- # echo ftrace > current_tracer
+ # echo function > current_tracer
# echo 1 > tracing_enabled
# usleep 1
# echo 0 > tracing_enabled
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 6c22d8a..60e2ce0 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -27,9 +27,7 @@ config HAVE_FUNCTION_GRAPH_TRACER
config HAVE_FUNCTION_GRAPH_FP_TEST
bool
help
- An arch may pass in a unique value (frame pointer) to both the
- entering and exiting of a function. On exit, the value is compared
- and if it does not match, then it will panic the kernel.
+ See Documentation/trace/ftrace-design.txt
config HAVE_FUNCTION_TRACE_MCOUNT_TEST
bool
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index edefe3b..8c1b2d2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -464,6 +464,8 @@ struct ring_buffer_iter {
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long head;
struct buffer_page *head_page;
+ struct buffer_page *cache_reader_page;
+ unsigned long cache_read;
u64 read_stamp;
};
@@ -2716,6 +2718,8 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
iter->read_stamp = cpu_buffer->read_stamp;
else
iter->read_stamp = iter->head_page->page->time_stamp;
+ iter->cache_reader_page = cpu_buffer->reader_page;
+ iter->cache_read = cpu_buffer->read;
}
/**
@@ -3060,13 +3064,22 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
struct ring_buffer_event *event;
int nr_loops = 0;
- if (ring_buffer_iter_empty(iter))
- return NULL;
-
cpu_buffer = iter->cpu_buffer;
buffer = cpu_buffer->buffer;
+ /*
+ * Check if someone performed a consuming read to
+ * the buffer. A consuming read invalidates the iterator
+ * and we need to reset the iterator in this case.
+ */
+ if (unlikely(iter->cache_read != cpu_buffer->read ||
+ iter->cache_reader_page != cpu_buffer->reader_page))
+ rb_iter_reset(iter);
+
again:
+ if (ring_buffer_iter_empty(iter))
+ return NULL;
+
/*
* We repeat when a timestamp is encountered.
* We can get multiple timestamps by nested interrupts or also
@@ -3081,6 +3094,11 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
if (rb_per_cpu_empty(cpu_buffer))
return NULL;
+ if (iter->head >= local_read(&iter->head_page->page->commit)) {
+ rb_inc_iter(iter);
+ goto again;
+ }
+
event = rb_iter_head_event(iter);
switch (event->type_len) {
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0df1b0f..eac6875 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -951,6 +951,11 @@ void trace_find_cmdline(int pid, char comm[])
return;
}
+ if (WARN_ON_ONCE(pid < 0)) {
+ strcpy(comm, "<XXX>");
+ return;
+ }
+
if (pid > PID_MAX_DEFAULT) {
strcpy(comm, "<...>");
return;
--
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