From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934484AbZLKEvN (ORCPT ); Thu, 10 Dec 2009 23:51:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760688AbZLKEvJ (ORCPT ); Thu, 10 Dec 2009 23:51:09 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:64420 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759512AbZLKEue (ORCPT ); Thu, 10 Dec 2009 23:50:34 -0500 X-Authority-Analysis: v=1.0 c=1 a=l-YuuxB_ykIA:10 a=20KFwNOVAAAA:8 a=meVymXHHAAAA:8 a=hlFY-uCeWgtk3xFhYXYA:9 a=4C9ePJDJVfqB0dpwzhoA:7 a=8EPRr_yyIyzlo364h6Vt5eHzN3YA:4 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.89.75 Message-Id: <20091211045039.718852320@goodmis.org> User-Agent: quilt/0.48-1 Date: Thu, 10 Dec 2009 23:50:04 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton Subject: [PATCH 1/2] [PATCH 1/2] ring-buffer: Use sync sched protection on ring buffer resizing References: <20091211045003.107725797@goodmis.org> Content-Disposition: inline; filename=0001-ring-buffer-Use-sync-sched-protection-on-ring-buffer.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt There was a comment in the ring buffer code that says the calling layers should prevent tracing or reading of the ring buffer while resizing. I have discovered that the tracers do not honor this arrangement. This patch moves the disabling and synchronizing the ring buffer to a higher layer during resizing. This guarantees that no writes are occurring while the resize takes place. Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 25 +++++++++---------------- 1 files changed, 9 insertions(+), 16 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index a1ca495..0d64c51 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1193,9 +1193,6 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) struct list_head *p; unsigned i; - atomic_inc(&cpu_buffer->record_disabled); - synchronize_sched(); - spin_lock_irq(&cpu_buffer->reader_lock); rb_head_page_deactivate(cpu_buffer); @@ -1214,9 +1211,6 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) spin_unlock_irq(&cpu_buffer->reader_lock); rb_check_pages(cpu_buffer); - - atomic_dec(&cpu_buffer->record_disabled); - } static void @@ -1227,9 +1221,6 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, struct list_head *p; unsigned i; - atomic_inc(&cpu_buffer->record_disabled); - synchronize_sched(); - spin_lock_irq(&cpu_buffer->reader_lock); rb_head_page_deactivate(cpu_buffer); @@ -1245,8 +1236,6 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, spin_unlock_irq(&cpu_buffer->reader_lock); rb_check_pages(cpu_buffer); - - atomic_dec(&cpu_buffer->record_disabled); } /** @@ -1254,11 +1243,6 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, * @buffer: the buffer to resize. * @size: the new size. * - * The tracer is responsible for making sure that the buffer is - * not being used while changing the size. - * Note: We may be able to change the above requirement by using - * RCU synchronizations. - * * Minimum size is 2 * BUF_PAGE_SIZE. * * Returns -1 on failure. @@ -1290,6 +1274,11 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) if (size == buffer_size) return size; + atomic_inc(&buffer->record_disabled); + + /* Make sure all writers are done with this buffer. */ + synchronize_sched(); + mutex_lock(&buffer->mutex); get_online_cpus(); @@ -1352,6 +1341,8 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) put_online_cpus(); mutex_unlock(&buffer->mutex); + atomic_dec(&buffer->record_disabled); + return size; free_pages: @@ -1361,6 +1352,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) } put_online_cpus(); mutex_unlock(&buffer->mutex); + atomic_dec(&buffer->record_disabled); return -ENOMEM; /* @@ -1370,6 +1362,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) out_fail: put_online_cpus(); mutex_unlock(&buffer->mutex); + atomic_dec(&buffer->record_disabled); return -1; } EXPORT_SYMBOL_GPL(ring_buffer_resize); -- 1.6.5