| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.14 142/159] ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer_update | Date | Fri, 23 Feb 2018 19:27:30 +0100 |
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4.14-stable review patch. If anyone has any objections, please let me know.
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From: Jiada Wang <jiada_wang@mentor.com>
[ Upstream commit 33f801366bdf3f8b67dfe325b84f4051a090d01e ]
Currently there is race condition between set of byte_pos and wrap it around when new buffer starts. If .pointer is called in-between it will result in inconsistent pointer position be returned from .pointer callback.
This patch increments buffer pointer atomically to avoid this issue.
Signed-off-by: Jiada Wang <jiada_wang@mentor.com> Reviewed-by: Takashi Sakamoto <takashi.sakamoto@miraclelinux.com> Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com> Signed-off-by: Mark Brown <broonie@kernel.org> Signed-off-by: Sasha Levin <alexander.levin@verizon.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- sound/soc/sh/rcar/ssi.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)
--- a/sound/soc/sh/rcar/ssi.c +++ b/sound/soc/sh/rcar/ssi.c @@ -449,25 +449,29 @@ static bool rsnd_ssi_pointer_update(stru int byte) { struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod); + bool ret = false; + int byte_pos; - ssi->byte_pos += byte; + byte_pos = ssi->byte_pos + byte; - if (ssi->byte_pos >= ssi->next_period_byte) { + if (byte_pos >= ssi->next_period_byte) { struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io); ssi->period_pos++; ssi->next_period_byte += ssi->byte_per_period; if (ssi->period_pos >= runtime->periods) { - ssi->byte_pos = 0; + byte_pos = 0; ssi->period_pos = 0; ssi->next_period_byte = ssi->byte_per_period; } - return true; + ret = true; } - return false; + WRITE_ONCE(ssi->byte_pos, byte_pos); + + return ret; } /* @@ -838,7 +842,7 @@ static int rsnd_ssi_pointer(struct rsnd_ struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod); struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io); - *pointer = bytes_to_frames(runtime, ssi->byte_pos); + *pointer = bytes_to_frames(runtime, READ_ONCE(ssi->byte_pos)); return 0; }
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