When a single thread is sending out data over the gadget serial port,
gs_start_tx() will be called both from the sender context and from the
write completion. Since the port lock is released before the packet is
queued, the order in which the URBs are submitted is not guaranteed.
E.g.
sending thread completion (interrupt)
gs_write()
LOCK
gs_write_complete()
LOCK (wait)
gs_start_tx()
req1 = list_entry(pool->next)
UNLOCK
LOCK (acquired)
gs_start_tx()
req2 = list_entry(pool->next)
UNLOCK
usb_ep_queue(req2)
usb_ep_queue(req1)
I.e., req2 is submitted before req1 but it contains the data that
comes after req1.
To reproduce, use SMP with sending thread and completion pinned to
different CPUs, or use PREEMPT_RT, and add the following delay just
before the call to usb_ep_queue():
if (port->write_started > 0 && !list_empty(pool))
udelay(1000);
To work around this problem, make sure that only one thread is running
through the gs_start_tx() loop with an extra flag write_busy. Since
gs_start_tx() is always called with the port lock held, no further
synchronisation is needed. The original caller will continue through
the loop when the request was successfully submitted.
Signed-off-by: Philip Oberstaller <Philip.Oberstaller@septentrio.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Use %ps for actual addresses, otherwise you'll get bad output
on arches like ppc64 where %pf expects a function descriptor
(which is not what __builtin_return_address returns).
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: linux-usb@vger.kernel.org
CC: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Remove the ttyGS PREFIX macro from u_serial.c and replace all occurences with
the hardcoded ttyGS string.
This macro was mostly used in a few debug/warning messages and a lot of
hardcoded ttyGS existed beneath. It may have been used for renaming the
tty, but if done so most debug messages would have ignored this.
Due to the fact the usage of this PREFIX in all debug calls would have
resulted in a hard to read/grep code it is removed completely.
Signed-off-by: Richard Leitner <richard.leitner@skidata.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
The drivers/usb/gadget directory contains many files.
Files which are related can be distributed into separate directories.
This patch moves the USB functions implementations into a separate directory.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
