On 27.12.2015 21:41, Soeren Moch wrote: > 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 <[email protected]> > Cc: [email protected] # 3.14+
Mauro, any news or comments on this? Since this is a real fix for broken behaviour, can you pick this up, please? Regards, Soeren > --- > Cc: Mauro Carvalho Chehab <[email protected]> > Cc: [email protected] > Cc: [email protected] > > 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; > }
