Em Sat, 7 May 2016 10:22:35 -0300 Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx> escreveu: > Hi Soeren, > > Em Sun, 7 Feb 2016 20:22:36 +0100 > Soeren Moch <smoch@xxxxxx> escreveu: > > > 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 <smoch@xxxxxx> > > > Cc: stable@xxxxxxxxxxxxxxx # 3.14+ > > > > Mauro, > > > > any news or comments on this? > > Since this is a real fix for broken behaviour, can you pick this up, please? > > The problem here is that I'm very reluctant to touch at the DVB core > without doing some tests myself, as things like locking can be > very sensible. In addition, it is good if other DVB developers could also test it. Even being sent for some time, until now, nobody else tested it. > > I'll try to find some time to take a look on it for Kernel 4.8, > but I'd like to reproduce the bug locally. > > Could you please provide me enough info to reproduce it (and > eventually some test MPEG-TS where you know this would happen)? > > I have two DekTek RF generators here, so I should be able to > play such TS and see what happens with and without the patch > on x86, arm32 and arm64. Ah, forgot to mention, but checkpatch.pl wants comments for the memory barriers: WARNING: memory barrier without comment #52: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:58: + return (rbuf->pread == smp_load_acquire(&rbuf->pwrite)); WARNING: memory barrier without comment #70: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:79: + avail = smp_load_acquire(&rbuf->pwrite) - rbuf->pread; WARNING: memory barrier without comment #79: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:89: + smp_store_release(&rbuf->pread, smp_load_acquire(&rbuf->pwrite)); WARNING: memory barrier without comment #87: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:96: + smp_store_release(&rbuf->pread, 0); WARNING: memory barrier without comment #88: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:97: + smp_store_release(&rbuf->pwrite, 0); WARNING: memory barrier without comment #97: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:123: + smp_store_release(&rbuf->pread, 0); WARNING: memory barrier without comment #103: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:128: + smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size); WARNING: memory barrier without comment #112: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:143: + smp_store_release(&rbuf->pread, 0); WARNING: memory barrier without comment #117: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:147: + smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size); WARNING: memory barrier without comment #126: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:162: + smp_store_release(&rbuf->pwrite, 0); WARNING: memory barrier without comment #130: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:165: + smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size); WARNING: memory barrier without comment #139: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:185: + smp_store_release(&rbuf->pwrite, 0); WARNING: memory barrier without comment #145: FILE: drivers/media/dvb-core/dvb_ringbuffer.c:190: + smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size); Thanks, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
