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drm/msm: use proper memory barriers for updating tail/head

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Fixes intermittent corruption of cmdstream dump.

Signed-off-by: Rob Clark <robdclark@gmail.com>
This commit is contained in:
Rob Clark 2017-10-02 10:28:37 -04:00
parent aa3c2ba1c3
commit f44001e263
1 changed files with 10 additions and 2 deletions
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12
drivers/gpu/drm/msm/msm_rd.c
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@ -111,10 +111,14 @@ static void rd_write(struct msm_rd_state *rd, const void *buf, int sz)
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, char __user *buf,
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);