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Commit d2a8cd3e authored by Alexander Usyskin's avatar Alexander Usyskin Committed by Greg Kroah-Hartman
Browse files

mei: remove support for broken parallel read 



commit cb97fbbcac15982406e0c74cd5512a8b6fcf10b3 upstream.

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.

Fixes: ff1586a7 ("mei: enqueue consecutive reads")
Signed-off-by: default avatarAlexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: default avatarTomas Winkler <tomas.winkler@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d6407e10

drivers/misc/mei/main.c

+26 −22
Original line number Diff line number Diff line
@@ -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 {

again:

	mutex_unlock(&dev->device_lock);



	if (wait_event_interruptible(cl->rx_wait,

					     (!list_empty(&cl->rd_completed)) ||

					     (!mei_cl_is_connected(cl)))) {



				     !list_empty(&cl->rd_completed) ||

				     !mei_cl_is_connected(cl))) {

		if (signal_pending(current))

			return -EINTR;

		return -ERESTARTSYS;

	}



	mutex_lock(&dev->device_lock);



	if (!mei_cl_is_connected(cl)) {

		rets = -ENODEV;

		goto out;

	}



	cb = mei_cl_read_cb(cl, file);

	} while (!cb);

	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;



		rets = 0;

		goto out;

	}



copy_buffer:

	/* now copy the data to user space */