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, 86 insertions, 0 deletions

diff --git a/Documentation/driver-api/nvdimm/firmware-activate.rst b/Documentation/driver-api/nvdimm/firmware-activate.rst
new file mode 100644
index 000000000..7ee7decbb
--- /dev/null
+++ b/Documentation/driver-api/nvdimm/firmware-activate.rst
@@ -0,0 +1,86 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
+NVDIMM Runtime Firmware Activation
+==================================
+
+Some persistent memory devices run a firmware locally on the device /
+"DIMM" to perform tasks like media management, capacity provisioning,
+and health monitoring. The process of updating that firmware typically
+involves a reboot because it has implications for in-flight memory
+transactions. However, reboots are disruptive and at least the Intel
+persistent memory platform implementation, described by the Intel ACPI
+DSM specification [1], has added support for activating firmware at
+runtime.
+
+A native sysfs interface is implemented in libnvdimm to allow platform
+to advertise and control their local runtime firmware activation
+capability.
+
+The libnvdimm bus object, ndbusX, implements an ndbusX/firmware/activate
+attribute that shows the state of the firmware activation as one of 'idle',
+'armed', 'overflow', and 'busy'.
+
+- idle:
+  No devices are set / armed to activate firmware
+
+- armed:
+  At least one device is armed
+
+- busy:
+  In the busy state armed devices are in the process of transitioning
+  back to idle and completing an activation cycle.
+
+- overflow:
+  If the platform has a concept of incremental work needed to perform
+  the activation it could be the case that too many DIMMs are armed for
+  activation. In that scenario the potential for firmware activation to
+  timeout is indicated by the 'overflow' state.
+
+The 'ndbusX/firmware/activate' property can be written with a value of
+either 'live', or 'quiesce'. A value of 'quiesce' triggers the kernel to
+run firmware activation from within the equivalent of the hibernation
+'freeze' state where drivers and applications are notified to stop their
+modifications of system memory. A value of 'live' attempts
+firmware activation without this hibernation cycle. The
+'ndbusX/firmware/activate' property will be elided completely if no
+firmware activation capability is detected.
+
+Another property 'ndbusX/firmware/capability' indicates a value of
+'live' or 'quiesce', where 'live' indicates that the firmware
+does not require or inflict any quiesce period on the system to update
+firmware. A capability value of 'quiesce' indicates that firmware does
+expect and injects a quiet period for the memory controller, but 'live'
+may still be written to 'ndbusX/firmware/activate' as an override to
+assume the risk of racing firmware update with in-flight device and
+application activity. The 'ndbusX/firmware/capability' property will be
+elided completely if no firmware activation capability is detected.
+
+The libnvdimm memory-device / DIMM object, nmemX, implements
+'nmemX/firmware/activate' and 'nmemX/firmware/result' attributes to
+communicate the per-device firmware activation state. Similar to the
+'ndbusX/firmware/activate' attribute, the 'nmemX/firmware/activate'
+attribute indicates 'idle', 'armed', or 'busy'. The state transitions
+from 'armed' to 'idle' when the system is prepared to activate firmware,
+firmware staged + state set to armed, and 'ndbusX/firmware/activate' is
+triggered. After that activation event the nmemX/firmware/result
+attribute reflects the state of the last activation as one of:
+
+- none:
+  No runtime activation triggered since the last time the device was reset
+
+- success:
+  The last runtime activation completed successfully.
+
+- fail:
+  The last runtime activation failed for device-specific reasons.
+
+- not_staged:
+  The last runtime activation failed due to a sequencing error of the
+  firmware image not being staged.
+
+- need_reset:
+  Runtime firmware activation failed, but the firmware can still be
+  activated via the legacy method of power-cycling the system.
+
+[1]: https://docs.pmem.io/persistent-memory/