The pvrusb2 driver was getting had by this scenario:
1. Task A calls kthread_stop() for task B.
2. Before exiting, then Task B calls kthread_stop() for task C.
The problem is, kthread_stop() wants to allocate an internal resource
to itself (i.e. acquire a lock), which won't be released until
kthread_stop() returns. But kthread_stop() won't return until task B
is dead. But task B won't die until it finishes its call to
kthread_stop() for task C, and that will block waiting on the resource
already allocated inside task A. Deadlock.
With the pvrusb2 driver, task A is the caller to pvr_exit(), task B is
the control thread run inside of pvrusb2-context.c, and task C is any
worker thread run inside of pvrusb2-hdw.c.
This problem got introduced by the previous threading setup change,
which was itself an attempt to fix a module tear-down race (which it
actually did fix). The lesson here is that a task being waited on as
part of a kthread_stop() simply cannot be allow to also issue a
kthread_stop() - or we make sure not to issue the enclosing
kthread_stop() until we know that the inner kthread_stop() has
completed first. The solution for the pvrusb2 driver is some hackish
code which changes the main control thread tear down into a two step
process. This then makes it possible to delay issuing the
kthread_stop() on the control thread until after we know that
everything has been torn down first. (And yes, we really need that
kthread_stop() because it's the only way to safely guarantee that a
module-referencing kernel thread has safely returned back out of the
module before we finally remove the module.)
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Earlier fix to handle DVB feed thread aborts was overly-aggressive.
We can take better advantage of what kthread_stop() can do. This
change simplifies things.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
If a disconnect happens before initialization is completed, the
pvrusb2 driver can accidentally touch dangling pointers. The whole
initialization function must be protected by the big_lock, and once
inside that lock, the initialization function should abort if it is
discovered that a disconnect has already taken place.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
The pvrusb2 driver - for basically forever - was not enforcing a
proper module tear-down. Kernel threads are used inside the driver
and all must be gone before the module can be safely removed. This
changeset reimplements a chunk of pvrusb2-context.c to enforce this
correctly. Unfortunately this is not a simple fix. The new
implementation also cuts back on kernel thread usage; instead of there
being 1 control thread per instance now it's just 1 control thread
shared by all instances. (By dropping to a single thread then the
module exit function can block on its shutdown and the thread itself
can monitor and cleanly shut down all of the other instances first.)
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Implement timed measurement of encoder operation for the first time it
is run. This allows the driver to note when the encoder has been run
successfully for at least 1/4 second. On top of that implement
various bits to ensure that the encoder has been run once before
digital streaming for OnAir devices. This is done via several core
state machine tweaks.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Some tuners seem to not work in digital mode unless the encoder is
healthy. Implement a device attribute to represent this flag and
modify the core state machines to enforce this requirement.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
If the device fails to stream, the feed thread will block forever
waiting for buffers. But while in this state it was not looking for
an exit condition from the driver DVB interface. This caused the
thread to jam. Implement a new stop flag (which will be set
appropriately) to tell the thread to stop.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
When the DVB interface is not compiled, the pvr2_dvb_props struct is
not available - so it really should be ifdef'ed out as well. This
didn't cause an error because in this context its usage was as an
opaque pointer. But it really shouldn't be present at all if DVB is
not enabled.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
The commands to start / stop USB streaming for an analog device are
fairly standard, owing to the fact that all supported devices
apparently started from the same common reference design. However
with digital mode, the commands seem to vary by vendor. This change
makes that variance more explicit. It also cleans up a related
problem for OnAir devices which prevented digital mode from working at
all.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Numerous places in the driver need to issue simple commands to the FX2
microcontroller (e.g. only 1 or 2 bytes, no reply needed). Previously
each place that did this, had to take lock, set up a central buffer,
and call the function to perform the handshake. This change puts
these steps into a single spot. This also has the effect of removing
the need to mess with the control lock from numerous places in the
code.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Implement a mechanism in the pvrusb2 driver for gathering statistics
on the stream buffering, including bytes transferred, buffers handled,
buffers in flight, etc. This is useful for debugging certain classes
of streaming issues and for determining if the buffer pool size is
generally correct for the driver.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Don't trigger a pathway state change if it's already been triggered
(eliminates some wasted processing and some debug output noise)
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Move pvr2_dvb_adapter usage out of the pvrusb2 driver core - it's
really private to the pvrusb2-dvb module and nothing outside of the
dvb implementation should care about it. Creation / destruction of
the pvr2_dvb_adapter instance is now contained entirely within
pvrusb2-dvb.c.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
In the end we'd like the dvb interface to always be present - even for
analog devices (via the mpeg encoder). However right now pvrusb2-dvb
won't operate correctly if the hardware doesn't have a digital tuner,
so don't initialize the DVB interface unless we know we have a digital
tuner.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Other pvrusb2-dvb changes have made the digital_up flag obsolete. So
kill it.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
