From 07d777fe8c3985bc83428c2866713c2d1b3d4129 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 22 Sep 2011 14:01:55 -0400 Subject: tracing: Add percpu buffers for trace_printk() Currently, trace_printk() uses a single buffer to write into to calculate the size and format needed to save the trace. To do this safely in an SMP environment, a spin_lock() is taken to only allow one writer at a time to the buffer. But this could also affect what is being traced, and add synchronization that would not be there otherwise. Ideally, using percpu buffers would be useful, but since trace_printk() is only used in development, having per cpu buffers for something never used is a waste of space. Thus, the use of the trace_bprintk() format section is changed to be used for static fmts as well as dynamic ones. Then at boot up, we can check if the section that holds the trace_printk formats is non-empty, and if it does contain something, then we know a trace_printk() has been added to the kernel. At this time the trace_printk per cpu buffers are allocated. A check is also done at module load time in case a module is added that contains a trace_printk(). Once the buffers are allocated, they are never freed. If you use a trace_printk() then you should know what you are doing. A buffer is made for each type of context: normal softirq irq nmi The context is checked and the appropriate buffer is used. This allows for totally lockless usage of trace_printk(), and they no longer even disable interrupts. Requested-by: Peter Zijlstra Signed-off-by: Steven Rostedt --- include/linux/kernel.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'include') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 645231c373c8..c0d34420a913 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -480,15 +480,16 @@ do { \ #define trace_printk(fmt, args...) \ do { \ + static const char *trace_printk_fmt \ + __attribute__((section("__trace_printk_fmt"))) = \ + __builtin_constant_p(fmt) ? fmt : NULL; \ + \ __trace_printk_check_format(fmt, ##args); \ - if (__builtin_constant_p(fmt)) { \ - static const char *trace_printk_fmt \ - __attribute__((section("__trace_printk_fmt"))) = \ - __builtin_constant_p(fmt) ? fmt : NULL; \ \ + if (__builtin_constant_p(fmt)) \ __trace_bprintk(_THIS_IP_, trace_printk_fmt, ##args); \ - } else \ - __trace_printk(_THIS_IP_, fmt, ##args); \ + else \ + __trace_printk(_THIS_IP_, fmt, ##args); \ } while (0) extern __printf(2, 3) -- cgit v1.2.3 From 438ced1720b584000a9e8a4349d1f6bb7ee3ad6d Mon Sep 17 00:00:00 2001 From: Vaibhav Nagarnaik Date: Thu, 2 Feb 2012 12:00:41 -0800 Subject: ring-buffer: Add per_cpu ring buffer control files Add a debugfs entry under per_cpu/ folder for each cpu called buffer_size_kb to control the ring buffer size for each CPU independently. If the global file buffer_size_kb is used to set size, the individual ring buffers will be adjusted to the given size. The buffer_size_kb will report the common size to maintain backward compatibility. If the buffer_size_kb file under the per_cpu/ directory is used to change buffer size for a specific CPU, only the size of the respective ring buffer is updated. When tracing/buffer_size_kb is read, it reports 'X' to indicate that sizes of per_cpu ring buffers are not equivalent. Link: http://lkml.kernel.org/r/1328212844-11889-1-git-send-email-vnagarnaik@google.com Cc: Frederic Weisbecker Cc: Michael Rubin Cc: David Sharp Cc: Justin Teravest Signed-off-by: Vaibhav Nagarnaik Signed-off-by: Steven Rostedt --- include/linux/ring_buffer.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 7be2e88f23fd..6c8835f74f79 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -96,9 +96,11 @@ __ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *k __ring_buffer_alloc((size), (flags), &__key); \ }) +#define RING_BUFFER_ALL_CPUS -1 + void ring_buffer_free(struct ring_buffer *buffer); -int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size); +int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, int cpu); void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val); @@ -129,7 +131,7 @@ ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts); void ring_buffer_iter_reset(struct ring_buffer_iter *iter); int ring_buffer_iter_empty(struct ring_buffer_iter *iter); -unsigned long ring_buffer_size(struct ring_buffer *buffer); +unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu); void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu); void ring_buffer_reset(struct ring_buffer *buffer); -- cgit v1.2.3 From 08d636b6d4fb80647fe8869ea1cd97b2c26a4751 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 16 Aug 2011 09:57:10 -0400 Subject: ftrace/x86: Have arch x86_64 use breakpoints instead of stop machine This method changes x86 to add a breakpoint to the mcount locations instead of calling stop machine. Now that iret can be handled by NMIs, we perform the following to update code: 1) Add a breakpoint to all locations that will be modified 2) Sync all cores 3) Update all locations to be either a nop or call (except breakpoint op) 4) Sync all cores 5) Remove the breakpoint with the new code. 6) Sync all cores [ Added updates that Masami suggested: Use unlikely(modifying_ftrace_code) in int3 trap to keep kprobes efficient. Don't use NOTIFY_* in ftrace handler in int3 as it is not a notifier. ] Cc: H. Peter Anvin Acked-by: Masami Hiramatsu Signed-off-by: Steven Rostedt --- include/linux/ftrace.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 72a6cabb4d5b..0b5590330bca 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -286,6 +286,12 @@ struct ftrace_rec_iter *ftrace_rec_iter_start(void); struct ftrace_rec_iter *ftrace_rec_iter_next(struct ftrace_rec_iter *iter); struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter); +#define for_ftrace_rec_iter(iter) \ + for (iter = ftrace_rec_iter_start(); \ + iter; \ + iter = ftrace_rec_iter_next(iter)) + + int ftrace_update_record(struct dyn_ftrace *rec, int enable); int ftrace_test_record(struct dyn_ftrace *rec, int enable); void ftrace_run_stop_machine(int command); -- cgit v1.2.3