drop queue-4.4/serial-pl011-fix-dma-flush_buffer.patch

diff --git a/queue-4.4/serial-pl011-fix-dma-flush_buffer.patch b/queue-4.4/serial-pl011-fix-dma-flush_buffer.patch
deleted file mode 100644 (file)
index 4847fdb..0000000
--- a/queue-4.4/serial-pl011-fix-dma-flush_buffer.patch
+++ /dev/null
@@ -1,73 +0,0 @@
-From f6a196477184b99a31d16366a8e826558aa11f6d Mon Sep 17 00:00:00 2001
-From: Vincent Whitchurch <vincent.whitchurch@axis.com>
-Date: Mon, 18 Nov 2019 10:25:47 +0100
-Subject: serial: pl011: Fix DMA ->flush_buffer()
-
-From: Vincent Whitchurch <vincent.whitchurch@axis.com>
-
-commit f6a196477184b99a31d16366a8e826558aa11f6d upstream.
-
-PL011's ->flush_buffer() implementation releases and reacquires the port
-lock.  Due to a race condition here, data can end up being added to the
-circular buffer but neither being discarded nor being sent out.  This
-leads to, for example, tcdrain(2) waiting indefinitely.
-
-Process A                       Process B
-
-uart_flush_buffer()
- - acquire lock
- - circ_clear
- - pl011_flush_buffer()
- -- release lock
- -- dmaengine_terminate_all()
-
-                                uart_write()
-                                - acquire lock
-                                - add chars to circ buffer
-                                - start_tx()
-                                -- start DMA
-                                - release lock
-
- -- acquire lock
- -- turn off DMA
- -- release lock
-
-                                // Data in circ buffer but DMA is off
-
-According to the comment in the code, the releasing of the lock around
-dmaengine_terminate_all() is to avoid a deadlock with the DMA engine
-callback.  However, since the time this code was written, the DMA engine
-API documentation seems to have been clarified to say that
-dmaengine_terminate_all() (in the identically implemented but
-differently named dmaengine_terminate_async() variant) does not wait for
-any running complete callback to be completed and can even be called
-from a complete callback.  So there is no possibility of deadlock if the
-DMA engine driver implements this API correctly.
-
-So we should be able to just remove this release and reacquire of the
-lock to prevent the aforementioned race condition.
-
-Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
-Cc: stable <stable@vger.kernel.org>
-Link: https://lore.kernel.org/r/20191118092547.32135-1-vincent.whitchurch@axis.com
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-
----
- drivers/tty/serial/amba-pl011.c |    6 ++----
- 1 file changed, 2 insertions(+), 4 deletions(-)
-
---- a/drivers/tty/serial/amba-pl011.c
-+++ b/drivers/tty/serial/amba-pl011.c
-@@ -694,10 +694,8 @@ __acquires(&uap->port.lock)
-       if (!uap->using_tx_dma)
-               return;
- 
--      /* Avoid deadlock with the DMA engine callback */
--      spin_unlock(&uap->port.lock);
--      dmaengine_terminate_all(uap->dmatx.chan);
--      spin_lock(&uap->port.lock);
-+      dmaengine_terminate_async(uap->dmatx.chan);
-+
-       if (uap->dmatx.queued) {
-               dma_unmap_sg(uap->dmatx.chan->device->dev, &uap->dmatx.sg, 1,
-                            DMA_TO_DEVICE);

diff --git a/queue-4.4/series b/queue-4.4/series
index 0836baf36ebe9abd4cf19f9c4164aa14be8c0b76..8284c5a4a9eba17d3f167cf072a8e88f0037b5f9 100644 (file)
--- a/queue-4.4/series
+++ b/queue-4.4/series
@@ -1,7 +1,6 @@
 x86-apic-32-avoid-bogus-ldr-warnings.patch
 usb-gadget-u_serial-add-missing-port-entry-locking.patch
 tty-serial-msm_serial-fix-flow-control.patch
-serial-pl011-fix-dma-flush_buffer.patch
 serial-serial_core-perform-null-checks-for-break_ctl-ops.patch
 serial-ifx6x60-add-missed-pm_runtime_disable.patch
 autofs-fix-a-leak-in-autofs_expire_indirect.patch