ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 56 insertions, 0 deletions

diff --git a/Documentation/gpu/panthor.rst b/Documentation/gpu/panthor.rst
new file mode 100644
index 000000000..7a8417412
--- /dev/null
+++ b/Documentation/gpu/panthor.rst
@@ -0,0 +1,56 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+=========================
+ drm/Panthor CSF driver
+=========================
+
+.. _panthor-usage-stats:
+
+Panthor DRM client usage stats implementation
+==============================================
+
+The drm/Panthor driver implements the DRM client usage stats specification as
+documented in :ref:`drm-client-usage-stats`.
+
+Example of the output showing the implemented key value pairs and entirety of
+the currently possible format options:
+
+::
+     pos:    0
+     flags:  02400002
+     mnt_id: 29
+     ino:    491
+     drm-driver:     panthor
+     drm-client-id:  10
+     drm-engine-panthor:     111110952750 ns
+     drm-cycles-panthor:     94439687187
+     drm-maxfreq-panthor:    1000000000 Hz
+     drm-curfreq-panthor:    1000000000 Hz
+     panthor-resident-memory:        10396 KiB
+     panthor-active-memory:  10396 KiB
+     drm-total-memory:       16480 KiB
+     drm-shared-memory:      0
+     drm-active-memory:      16200 KiB
+     drm-resident-memory:    16480 KiB
+     drm-purgeable-memory:   0
+
+Possible `drm-engine-` key names are: `panthor`.
+`drm-curfreq-` values convey the current operating frequency for that engine.
+
+Users must bear in mind that engine and cycle sampling are disabled by default,
+because of power saving concerns. `fdinfo` users and benchmark applications which
+query the fdinfo file must make sure to toggle the job profiling status of the
+driver by writing into the appropriate sysfs node::
+
+    echo <N> > /sys/bus/platform/drivers/panthor/[a-f0-9]*.gpu/profiling
+
+Where `N` is a bit mask where cycle and timestamp sampling are respectively
+enabled by the first and second bits.
+
+Possible `panthor-*-memory` keys are: `active` and `resident`.
+These values convey the sizes of the internal driver-owned shmem BO's that
+aren't exposed to user-space through a DRM handle, like queue ring buffers,
+sync object arrays and heap chunks. Because they are all allocated and pinned
+at creation time, only `panthor-resident-memory` is necessary to tell us their
+size. `panthor-active-memory` shows the size of kernel BO's associated with
+VM's and groups currently being scheduled for execution by the GPU.