The i915_vblank_swap() function schedules an automatic buffer swap
upon receipt of the vertical sync interrupt. Such an operation is
lengthy so it can't be allowed to happen in normal interrupt context,
thus the DRM implements this by scheduling the work in a kernel
softirq-scheduled tasklet. In order for the buffer swap to work
safely, the DRM's central lock must be taken, via a call to
drm_lock_take() located in drivers/char/drm/drm_irq.c within the
function drm_locked_tasklet_func(). The lock-taking logic uses a
non-interrupt-blocking spinlock to implement the manipulations needed
to take the lock. This semantic would be safe if all attempts to use
the spinlock only happen from process context. However this buffer
swap happens from softirq context which is really a form of interrupt
context. Thus we have an unsafe situation, in that
drm_locked_tasklet_func() can block on a spinlock already taken by a
thread in process context which will never get scheduled again because
of the blocked softirq tasklet. This wedges the kernel hard.
To trigger this bug, run a dual-head cloned mode configuration which
uses the i915 drm, then execute an opengl application which
synchronizes buffer swaps against the vertical sync interrupt. In my
testing, a lockup always results after running anywhere from 5 minutes
to an hour and a half. I believe dual-head is needed to really
trigger the problem because then the vertical sync interrupt handling
is no longer predictable (due to being interrupt-sourced from two
different heads running at different speeds). This raises the
probability of the tasklet trying to run while the userspace DRI is
doing things to the GPU (and manipulating the DRM lock).
The fix is to change the relevant spinlock semantics to be the
interrupt-blocking form. After this change I am no longer able to
trigger the lockup; the longest test run so far was 20 hours (test
stopped after that point).
Note: I have examined the places where this spinlock is being
employed; all are reasonably short bounded sequences and should be
suitable for interrupts being blocked without impacting overall kernel
interrupt response latency.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
The task_struct->pid member is going to be deprecated, so start
using the helpers (task_pid_nr/task_pid_vnr/task_pid_nr_ns) in
the kernel.
The first thing to start with is the pid, printed to dmesg - in
this case we may safely use task_pid_nr(). Besides, printks produce
more (much more) than a half of all the explicit pid usage.
[akpm@linux-foundation.org: git-drm went and changed lots of stuff]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The data is now in kernel space, copied in/out as appropriate according to t
This results in DRM_COPY_{TO,FROM}_USER going away, and error paths to deal
with those failures. This also means that XFree86 4.2.0 support for i810 DR
is lost.
Signed-off-by: Dave Airlie <airlied@linux.ie>
As a fallout, replace filp storage with file_priv storage for "unique
identifier of a client" all over the DRM. There is a 1:1 mapping, so this
should be a noop. This could be a minor performance improvement, as everyth
on Linux dereferenced filp to get file_priv anyway, while only the mmap ioct
went the other direction.
Signed-off-by: Dave Airlie <airlied@linux.ie>
This was used to make all ioctl handlers return -errno on linux and errno on
*BSD. Instead, just return -errno in shared code, and flip sign on return f
shared code to *BSD code.
Signed-off-by: Dave Airlie <airlied@linux.ie>
This moves a bunch of typedefs into a !defined __KERNEL__ to keep userspace
API compatiblity, it changes all internal usages to structs/enum/unions.
Signed-off-by: Dave Airlie <airlied@linux.ie>
Bugzilla Bug #9457
Add refcounting of user waiters to the DRM hardware lock, so that we can use
DRM_LOCK_CONT flag more conservatively.
Also add a kernel waiter refcount that if nonzero transfers the lock for the
kernel context when it is released. This is useful when waiting for idle and can be used for very simple fence object driver implementations for the new memory manager
Signed-off-by: Dave Airlie <airlied@linux.ie>
This patch pull in a lot of changes from CVS to the main core DRM,
and updates the radeon driver to 1.21.0 that supports r300 texrect
and radeon card type ioctl.
Signed-off-by: Dave Airlie <airlied@linux.ie>
A fix for a locking bug which is triggered when a client tries to lock with
flag DMA_QUIESCENT (typically the X server), but gets interrupted by a signal.
The locking IOCTL should then return an error, but if DMA_QUIESCENT succeeds
it returns 0, and the client falsely thinks it has the lock. In addition
The client waits for DMA_QUISCENT and possibly DMA_READY without having the lock.
From: Thomas Hellstrom
Signed-off-by: Dave Airlie <airlied@linux.ie>
I've been threatening this for a while, so no point hanging around.
This lindents the DRM code which was always really bad in tabbing department.
I've also fixed some misnamed files in comments and removed some trailing
whitespace.
Signed-off-by: Dave Airlie <airlied@linux.ie>
This patch contains the following cleanups:
- make needlessly global functions static
- remove the following unused global functions:
- drm_fops.c: drm_read
- i915_dma.c: i915_do_cleanup_pageflip
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Dave Airlie <airlied@linux.ie>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
