From 884bfe89a462fcc85c8abd96171519cf2fe70929 Mon Sep 17 00:00:00 2001 From: Slava Pestov Date: Fri, 15 Jul 2011 14:23:58 -0700 Subject: ring-buffer: Add a 'dropped events' counter The existing 'overrun' counter is incremented when the ring buffer wraps around, with overflow on (the default). We wanted a way to count requests lost from the buffer filling up with overflow off, too. I decided to add a new counter instead of retro-fitting the existing one because it seems like a different statistic to count conceptually, and also because of how the code was structured. Link: http://lkml.kernel.org/r/1310765038-26399-1-git-send-email-slavapestov@google.com Signed-off-by: Slava Pestov Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 41 +++++++++++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 6 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b979426d16c6..0ebeb1d76ddf 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -460,9 +460,10 @@ struct ring_buffer_per_cpu { unsigned long lost_events; unsigned long last_overrun; local_t entries_bytes; - local_t commit_overrun; - local_t overrun; local_t entries; + local_t overrun; + local_t commit_overrun; + local_t dropped_events; local_t committing; local_t commits; unsigned long read; @@ -2155,8 +2156,10 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, * If we are not in overwrite mode, * this is easy, just stop here. */ - if (!(buffer->flags & RB_FL_OVERWRITE)) + if (!(buffer->flags & RB_FL_OVERWRITE)) { + local_inc(&cpu_buffer->dropped_events); goto out_reset; + } ret = rb_handle_head_page(cpu_buffer, tail_page, @@ -2995,7 +2998,8 @@ unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); /** - * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer + * ring_buffer_overrun_cpu - get the number of overruns caused by the ring + * buffer wrapping around (only if RB_FL_OVERWRITE is on). * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */ @@ -3015,7 +3019,9 @@ unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); /** - * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits + * ring_buffer_commit_overrun_cpu - get the number of overruns caused by + * commits failing due to the buffer wrapping around while there are uncommitted + * events, such as during an interrupt storm. * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */ @@ -3035,6 +3041,28 @@ ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu) } EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); +/** + * ring_buffer_dropped_events_cpu - get the number of dropped events caused by + * the ring buffer filling up (only if RB_FL_OVERWRITE is off). + * @buffer: The ring buffer + * @cpu: The per CPU buffer to get the number of overruns from + */ +unsigned long +ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + unsigned long ret; + + if (!cpumask_test_cpu(cpu, buffer->cpumask)) + return 0; + + cpu_buffer = buffer->buffers[cpu]; + ret = local_read(&cpu_buffer->dropped_events); + + return ret; +} +EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); + /** * ring_buffer_entries - get the number of entries in a buffer * @buffer: The ring buffer @@ -3864,9 +3892,10 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) local_set(&cpu_buffer->reader_page->page->commit, 0); cpu_buffer->reader_page->read = 0; - local_set(&cpu_buffer->commit_overrun, 0); local_set(&cpu_buffer->entries_bytes, 0); local_set(&cpu_buffer->overrun, 0); + local_set(&cpu_buffer->commit_overrun, 0); + local_set(&cpu_buffer->dropped_events, 0); local_set(&cpu_buffer->entries, 0); local_set(&cpu_buffer->committing, 0); local_set(&cpu_buffer->commits, 0); -- cgit v1.2.3 From 01e3e710a9265fb7092efd67243d7b6dd6e2548a Mon Sep 17 00:00:00 2001 From: David Sharp Date: Thu, 7 Jun 2012 16:46:24 -0700 Subject: tracing: Trivial cleanup Remove ftrace_format_syscall() declaration; it is neither defined nor used. Also update a comment and formatting. Link: http://lkml.kernel.org/r/1339112785-21806-1-git-send-email-vnagarnaik@google.com Signed-off-by: David Sharp Signed-off-by: Vaibhav Nagarnaik Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 0ebeb1d76ddf..23a384b92512 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1821,7 +1821,7 @@ rb_add_time_stamp(struct ring_buffer_event *event, u64 delta) } /** - * ring_buffer_update_event - update event type and data + * rb_update_event - update event type and data * @event: the even to update * @type: the type of event * @length: the size of the event field in the ring buffer @@ -2723,8 +2723,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); * and not the length of the event which would hold the header. */ int ring_buffer_write(struct ring_buffer *buffer, - unsigned long length, - void *data) + unsigned long length, + void *data) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; -- cgit v1.2.3 From 50ecf2c3afead23a05227ab004e4212eca08c207 Mon Sep 17 00:00:00 2001 From: Yoshihiro YUNOMAE Date: Thu, 11 Oct 2012 16:27:54 -0700 Subject: ring-buffer: Change unsigned long type of ring_buffer_oldest_event_ts() to u64 ring_buffer_oldest_event_ts() should return a value of u64 type, because ring_buffer_per_cpu->buffer_page->buffer_data_page->time_stamp is u64 type. Link: http://lkml.kernel.org/r/1349998076-15495-5-git-send-email-dhsharp@google.com Cc: Frederic Weisbecker Cc: Vaibhav Nagarnaik Signed-off-by: Yoshihiro YUNOMAE Signed-off-by: David Sharp Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 23a384b92512..3c7834c24e54 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2932,12 +2932,12 @@ rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) * @buffer: The ring buffer * @cpu: The per CPU buffer to read from. */ -unsigned long ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) +u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) { unsigned long flags; struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage; - unsigned long ret; + u64 ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; -- cgit v1.2.3 From 54f7be5b831254199522523ccab4c3d954bbf576 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 29 Nov 2012 22:27:22 -0500 Subject: ring-buffer: Fix NULL pointer if rb_set_head_page() fails The function rb_set_head_page() searches the list of ring buffer pages for a the page that has the HEAD page flag set. If it does not find it, it will do a WARN_ON(), disable the ring buffer and return NULL, as this should never happen. But if this bug happens to happen, not all callers of this function can handle a NULL pointer being returned from it. That needs to be fixed. Cc: stable@vger.kernel.org # 3.0+ Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b979426d16c6..ec01803e0a55 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1396,6 +1396,8 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) struct list_head *head_page_with_bit; head_page = &rb_set_head_page(cpu_buffer)->list; + if (!head_page) + break; prev_page = head_page->prev; first_page = pages->next; @@ -2934,7 +2936,7 @@ unsigned long ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) unsigned long flags; struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage; - unsigned long ret; + unsigned long ret = 0; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; @@ -2949,7 +2951,8 @@ unsigned long ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) bpage = cpu_buffer->reader_page; else bpage = rb_set_head_page(cpu_buffer); - ret = bpage->page->time_stamp; + if (bpage) + ret = bpage->page->time_stamp; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return ret; @@ -3260,6 +3263,8 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) * Splice the empty reader page into the list around the head. */ reader = rb_set_head_page(cpu_buffer); + if (!reader) + goto out; cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); cpu_buffer->reader_page->list.prev = reader->list.prev; -- cgit v1.2.3 From 9366c1ba13fbc41bdb57702e75ca4382f209c82f Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 29 Nov 2012 22:31:16 -0500 Subject: ring-buffer: Fix race between integrity check and readers The function rb_check_pages() was added to make sure the ring buffer's pages were sane. This check is done when the ring buffer size is modified as well as when the iterator is released (closing the "trace" file), as that was considered a non fast path and a good place to do a sanity check. The problem is that the check does not have any locks around it. If one process were to read the trace file, and another were to read the raw binary file, the check could happen while the reader is reading the file. The issues with this is that the check requires to clear the HEAD page before doing the full check and it restores it afterward. But readers require the HEAD page to exist before it can read the buffer, otherwise it gives a nasty warning and disables the buffer. By adding the reader lock around the check, this keeps the race from happening. Cc: stable@vger.kernel.org # 3.6 Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'kernel/trace/ring_buffer.c') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index ec01803e0a55..4cb5e5147165 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3783,12 +3783,17 @@ void ring_buffer_read_finish(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; + unsigned long flags; /* * Ring buffer is disabled from recording, here's a good place - * to check the integrity of the ring buffer. + * to check the integrity of the ring buffer. + * Must prevent readers from trying to read, as the check + * clears the HEAD page and readers require it. */ + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_check_pages(cpu_buffer); + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); atomic_dec(&cpu_buffer->record_disabled); atomic_dec(&cpu_buffer->buffer->resize_disabled); -- cgit v1.2.3