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tty: hvc: hvc_write() may sleep

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Rework the hvc_write loop to drop and re-take the spinlock on each
iteration, add a cond_resched. Don't bother with an initial hvc_push
initially, which makes the logic simpler -- just do a hvc_push on
each time around the loop.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2018-05-01 00:55:56 +10:00 committed by Michael Ellerman
parent cfb5946b55
commit 550ddadcc7
1 changed files with 20 additions and 14 deletions
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34
drivers/tty/hvc/hvc_console.c
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@ -493,23 +493,29 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count
if (hp->port.count <= 0)
return -EIO;
spin_lock_irqsave(&hp->lock, flags);
while (count > 0) {
spin_lock_irqsave(&hp->lock, flags);
/* Push pending writes */
if (hp->n_outbuf > 0)
hvc_push(hp);
rsize = hp->outbuf_size - hp->n_outbuf;
while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
if (rsize > count)
rsize = count;
memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
count -= rsize;
buf += rsize;
hp->n_outbuf += rsize;
written += rsize;
hvc_push(hp);
if (rsize) {
if (rsize > count)
rsize = count;
memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
count -= rsize;
buf += rsize;
hp->n_outbuf += rsize;
written += rsize;
}
if (hp->n_outbuf > 0)
hvc_push(hp);
spin_unlock_irqrestore(&hp->lock, flags);
if (count)
cond_resched();
}
spin_unlock_irqrestore(&hp->lock, flags);
/*
* Racy, but harmless, kick thread if there is still pending data.