Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753503AbYL2Hdf (ORCPT ); Mon, 29 Dec 2008 02:33:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752320AbYL2Hd1 (ORCPT ); Mon, 29 Dec 2008 02:33:27 -0500 Received: from smarthost1.greenhost.nl ([195.190.28.78]:49431 "EHLO smarthost1.samage.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750862AbYL2Hd0 (ORCPT ); Mon, 29 Dec 2008 02:33:26 -0500 From: Indan Zupancic To: Steven Rostedt , Ingo Molnar Cc: linux-kernel@vger.kernel.org, Indan Zupancic Subject: [PATCH] Fix race in ring_buffer_consume(): Replace ring_buffer_consume and ring_buffer_peek with ring_buffer_get_event Date: Mon, 29 Dec 2008 18:34:04 +1100 Message-Id: <1230536044-14847-1-git-send-email-indan@nul.nu> X-Mailer: git-send-email 1.6.0.6 In-Reply-To: <54882.124.179.251.206.1230523141.squirrel@secure.greenhost.nl> References: <54882.124.179.251.206.1230523141.squirrel@secure.greenhost.nl> X-Spam-Score: 0.1 X-Scan-Signature: d03c6668c40393d71259a55b271b8ef3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5922 Lines: 168 Original mail was mangled, patch resent via git. Signed-off-by: Indan Zupancic --- include/linux/ring_buffer.h | 4 +--- kernel/trace/ring_buffer.c | 39 ++++++++------------------------------- kernel/trace/trace.c | 15 ++++++++------- kernel/trace/trace_selftest.c | 2 +- 4 files changed, 18 insertions(+), 42 deletions(-) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index e097c2e..d9320bd 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -83,9 +83,7 @@ int ring_buffer_write(struct ring_buffer *buffer, unsigned long length, void *data); struct ring_buffer_event * -ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts); -struct ring_buffer_event * -ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts); +ring_buffer_get_event(struct ring_buffer *buffer, int cpu, u64 *ts, int consume); struct ring_buffer_iter * ring_buffer_read_start(struct ring_buffer *buffer, int cpu); diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 668bbb5..d4e5dbc 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1727,16 +1727,18 @@ static void rb_advance_iter(struct ring_buffer_iter *iter) } /** - * ring_buffer_peek - peek at the next event to be read + * ring_buffer_get_event - get the next event to be read * @buffer: The ring buffer to read * @cpu: The cpu to peak at * @ts: The timestamp counter of this event. + * @consume: Whether the event should be consumed. + * If true, sequential reads will keep returning a different event, + * and eventually empty the ring buffer if the producer is slower. * - * This will return the event that will be read next, but does - * not consume the data. + * This will return the event that will be read next. */ struct ring_buffer_event * -ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) +ring_buffer_get_event(struct ring_buffer *buffer, int cpu, u64 *ts, int consume) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; @@ -1789,6 +1791,8 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) *ts = cpu_buffer->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts); } + if (consume) + rb_advance_reader(cpu_buffer); return event; default: @@ -1869,33 +1873,6 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) } /** - * ring_buffer_consume - return an event and consume it - * @buffer: The ring buffer to get the next event from - * - * Returns the next event in the ring buffer, and that event is consumed. - * Meaning, that sequential reads will keep returning a different event, - * and eventually empty the ring buffer if the producer is slower. - */ -struct ring_buffer_event * -ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) -{ - struct ring_buffer_per_cpu *cpu_buffer; - struct ring_buffer_event *event; - - if (!cpu_isset(cpu, buffer->cpumask)) - return NULL; - - event = ring_buffer_peek(buffer, cpu, ts); - if (!event) - return NULL; - - cpu_buffer = buffer->buffers[cpu]; - rb_advance_reader(cpu_buffer); - - return event; -} - -/** * ring_buffer_read_start - start a non consuming read of the buffer * @buffer: The ring buffer to read from * @cpu: The cpu buffer to iterate over diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index d86e325..f1329ed 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -938,7 +938,7 @@ peek_next_entry(struct trace_iterator *iter, int cpu, u64 *ts) if (buf_iter) event = ring_buffer_iter_peek(buf_iter, ts); else - event = ring_buffer_peek(iter->tr->buffer, cpu, ts); + event = ring_buffer_get_event(iter->tr->buffer, cpu, ts, 0); ftrace_enable_cpu(); @@ -1002,7 +1002,7 @@ static void trace_consume(struct trace_iterator *iter) { /* Don't allow ftrace to trace into the ring buffers */ ftrace_disable_cpu(); - ring_buffer_consume(iter->tr->buffer, iter->cpu, &iter->ts); + ring_buffer_get_event(iter->tr->buffer, iter->cpu, &iter->ts, 1); ftrace_enable_cpu(); } @@ -1310,8 +1310,9 @@ void trace_seq_print_cont(struct trace_seq *s, struct trace_iterator *iter) struct trace_entry *ent; struct trace_field_cont *cont; bool ok = true; + int cpu = iter->cpu; - ent = peek_next_entry(iter, iter->cpu, NULL); + ent = peek_next_entry(iter, cpu, NULL); if (!ent || ent->type != TRACE_CONT) { trace_seq_putc(s, '\n'); return; @@ -1324,14 +1325,14 @@ void trace_seq_print_cont(struct trace_seq *s, struct trace_iterator *iter) ftrace_disable_cpu(); - if (iter->buffer_iter[iter->cpu]) - ring_buffer_read(iter->buffer_iter[iter->cpu], NULL); + if (iter->buffer_iter[cpu]) + ring_buffer_read(iter->buffer_iter[cpu], NULL); else - ring_buffer_consume(iter->tr->buffer, iter->cpu, NULL); + ring_buffer_get_event(iter->tr->buffer, cpu, NULL, 1); ftrace_enable_cpu(); - ent = peek_next_entry(iter, iter->cpu, NULL); + ent = peek_next_entry(iter, cpu, NULL); } while (ent && ent->type == TRACE_CONT); if (!ok) diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c index 90bc752..3894989 100644 --- a/kernel/trace/trace_selftest.c +++ b/kernel/trace/trace_selftest.c @@ -23,7 +23,7 @@ static int trace_test_buffer_cpu(struct trace_array *tr, int cpu) struct ring_buffer_event *event; struct trace_entry *entry; - while ((event = ring_buffer_consume(tr->buffer, cpu, NULL))) { + while ((event = ring_buffer_get_event(tr->buffer, cpu, NULL, 1))) { entry = ring_buffer_event_data(event); if (!trace_valid_entry(entry)) { -- 1.6.0.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/