From cb97fbbcac15982406e0c74cd5512a8b6fcf10b3 Mon Sep 17 00:00:00 2001 From: Alexander Usyskin Date: Wed, 8 Feb 2017 00:41:45 +0200 Subject: [PATCH] mei: remove support for broken parallel read Parallel reads from multiple threads on a file descriptor are not well defined and racy. It is safer to return to original behavior and simply fail the additional read. The solution is to remove request for next read credit. Cc: #4.9 Fixes: ff1586a7ea57 ("mei: enqueue consecutive reads") Signed-off-by: Alexander Usyskin Signed-off-by: Tomas Winkler Signed-off-by: Greg Kroah-Hartman --- drivers/misc/mei/main.c | 48 ++++++++++++++++++++++++++---------------------- 1 file changed, 26 insertions(+), 22 deletions(-) diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c index e1bf544..9d0b705 100644 --- a/drivers/misc/mei/main.c +++ b/drivers/misc/mei/main.c @@ -182,32 +182,36 @@ static ssize_t mei_read(struct file *file, char __user *ubuf, goto out; } - if (rets == -EBUSY && - !mei_cl_enqueue_ctrl_wr_cb(cl, length, MEI_FOP_READ, file)) { - rets = -ENOMEM; - goto out; - } - do { - mutex_unlock(&dev->device_lock); - - if (wait_event_interruptible(cl->rx_wait, - (!list_empty(&cl->rd_completed)) || - (!mei_cl_is_connected(cl)))) { +again: + mutex_unlock(&dev->device_lock); + if (wait_event_interruptible(cl->rx_wait, + !list_empty(&cl->rd_completed) || + !mei_cl_is_connected(cl))) { + if (signal_pending(current)) + return -EINTR; + return -ERESTARTSYS; + } + mutex_lock(&dev->device_lock); - if (signal_pending(current)) - return -EINTR; - return -ERESTARTSYS; - } + if (!mei_cl_is_connected(cl)) { + rets = -ENODEV; + goto out; + } - mutex_lock(&dev->device_lock); - if (!mei_cl_is_connected(cl)) { - rets = -ENODEV; - goto out; - } + cb = mei_cl_read_cb(cl, file); + if (!cb) { + /* + * For amthif all the waiters are woken up, + * but only fp with matching cb->fp get the cb, + * the others have to return to wait on read. + */ + if (cl == &dev->iamthif_cl) + goto again; - cb = mei_cl_read_cb(cl, file); - } while (!cb); + rets = 0; + goto out; + } copy_buffer: /* now copy the data to user space */ -- 2.7.4