From: Rob Clark Date: Mon, 2 Oct 2017 10:28:37 -0400 Subject: drm/msm: use proper memory barriers for updating tail/head Git-commit: f44001e2637138d9d506efe8da67011f8170e860 Patch-mainline: v4.14-rc5 References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166 Fixes intermittent corruption of cmdstream dump. Signed-off-by: Rob Clark Acked-by: Petr Tesarik --- drivers/gpu/drm/msm/msm_rd.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/msm/msm_rd.c +++ b/drivers/gpu/drm/msm/msm_rd.c @@ -111,10 +111,14 @@ static void rd_write(struct msm_rd_state wait_event(rd->fifo_event, circ_space(&rd->fifo) > 0); + /* Note that smp_load_acquire() is not strictly required + * as CIRC_SPACE_TO_END() does not access the tail more + * than once. + */ n = min(sz, circ_space_to_end(&rd->fifo)); memcpy(fptr, ptr, n); - fifo->head = (fifo->head + n) & (BUF_SZ - 1); + smp_store_release(&fifo->head, (fifo->head + n) & (BUF_SZ - 1)); sz -= n; ptr += n; @@ -145,13 +149,17 @@ static ssize_t rd_read(struct file *file if (ret) goto out; + /* Note that smp_load_acquire() is not strictly required + * as CIRC_CNT_TO_END() does not access the head more than + * once. + */ n = min_t(int, sz, circ_count_to_end(&rd->fifo)); if (copy_to_user(buf, fptr, n)) { ret = -EFAULT; goto out; } - fifo->tail = (fifo->tail + n) & (BUF_SZ - 1); + smp_store_release(&fifo->tail, (fifo->tail + n) & (BUF_SZ - 1)); *ppos += n; wake_up_all(&rd->fifo_event);