From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mout.web.de ([212.227.17.12]:60348 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966012AbcCPNmr (ORCPT ); Wed, 16 Mar 2016 09:42:47 -0400 Subject: [PATCH RESEND] media: dvb_ringbuffer: Add memory barriers To: Mauro Carvalho Chehab References: <1451248920-4935-1-git-send-email-smoch@web.de> Cc: Soeren Moch , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org From: Soeren Moch Message-ID: <56E962C2.4060001@web.de> Date: Wed, 16 Mar 2016 14:42:26 +0100 MIME-Version: 1.0 In-Reply-To: <1451248920-4935-1-git-send-email-smoch@web.de> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Implement memory barriers according to Documentation/circular-buffers.txt: - use smp_store_release() to update ringbuffer read/write pointers - use smp_load_acquire() to load write pointer on reader side - use ACCESS_ONCE() to load read pointer on writer side This fixes data stream corruptions observed e.g. on an ARM Cortex-A9 quad core system with different types (PCI, USB) of DVB tuners. Signed-off-by: Soeren Moch Cc: stable@vger.kernel.org # 3.14+ --- Cc: Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org Cc: linux-kernel@vger.kernel.org Since smp_store_release() and smp_load_acquire() were introduced in linux-3.14, a 3.14+ stable tag was added. Is it desired to apply a similar patch to older stable kernels? --- drivers/media/dvb-core/dvb_ringbuffer.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/drivers/media/dvb-core/dvb_ringbuffer.c b/drivers/media/dvb-core/dvb_ringbuffer.c index 1100e98..58b5968 100644 --- a/drivers/media/dvb-core/dvb_ringbuffer.c +++ b/drivers/media/dvb-core/dvb_ringbuffer.c @@ -55,7 +55,7 @@ void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len) int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf) { - return (rbuf->pread==rbuf->pwrite); + return (rbuf->pread == smp_load_acquire(&rbuf->pwrite)); } @@ -64,7 +64,7 @@ ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf) { ssize_t free; - free = rbuf->pread - rbuf->pwrite; + free = ACCESS_ONCE(rbuf->pread) - rbuf->pwrite; if (free <= 0) free += rbuf->size; return free-1; @@ -76,7 +76,7 @@ ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf) { ssize_t avail; - avail = rbuf->pwrite - rbuf->pread; + avail = smp_load_acquire(&rbuf->pwrite) - rbuf->pread; if (avail < 0) avail += rbuf->size; return avail; @@ -86,14 +86,15 @@ ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf) void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf) { - rbuf->pread = rbuf->pwrite; + smp_store_release(&rbuf->pread, smp_load_acquire(&rbuf->pwrite)); rbuf->error = 0; } EXPORT_SYMBOL(dvb_ringbuffer_flush); void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf) { - rbuf->pread = rbuf->pwrite = 0; + smp_store_release(&rbuf->pread, 0); + smp_store_release(&rbuf->pwrite, 0); rbuf->error = 0; } @@ -119,12 +120,12 @@ ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer *rbuf, u8 __user *buf, si return -EFAULT; buf += split; todo -= split; - rbuf->pread = 0; + smp_store_release(&rbuf->pread, 0); } if (copy_to_user(buf, rbuf->data+rbuf->pread, todo)) return -EFAULT; - rbuf->pread = (rbuf->pread + todo) % rbuf->size; + smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size); return len; } @@ -139,11 +140,11 @@ void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf, size_t len) memcpy(buf, rbuf->data+rbuf->pread, split); buf += split; todo -= split; - rbuf->pread = 0; + smp_store_release(&rbuf->pread, 0); } memcpy(buf, rbuf->data+rbuf->pread, todo); - rbuf->pread = (rbuf->pread + todo) % rbuf->size; + smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size); } @@ -158,10 +159,10 @@ ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf, size_t memcpy(rbuf->data+rbuf->pwrite, buf, split); buf += split; todo -= split; - rbuf->pwrite = 0; + smp_store_release(&rbuf->pwrite, 0); } memcpy(rbuf->data+rbuf->pwrite, buf, todo); - rbuf->pwrite = (rbuf->pwrite + todo) % rbuf->size; + smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size); return len; } @@ -181,12 +182,12 @@ ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf, return len - todo; buf += split; todo -= split; - rbuf->pwrite = 0; + smp_store_release(&rbuf->pwrite, 0); } status = copy_from_user(rbuf->data+rbuf->pwrite, buf, todo); if (status) return len - todo; - rbuf->pwrite = (rbuf->pwrite + todo) % rbuf->size; + smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size); return len; } -- 1.9.1