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, 238 insertions, 0 deletions

diff --git a/Documentation/firmware-guide/acpi/method-tracing.rst b/Documentation/firmware-guide/acpi/method-tracing.rst
new file mode 100644
index 000000000..6ab6c0964
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/method-tracing.rst
@@ -0,0 +1,238 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+=====================
+ACPICA Trace Facility
+=====================
+
+:Copyright: |copy| 2015, Intel Corporation
+:Author: Lv Zheng <lv.zheng@intel.com>
+
+
+Abstract
+========
+This document describes the functions and the interfaces of the
+method tracing facility.
+
+Functionalities and usage examples
+==================================
+
+ACPICA provides method tracing capability. And two functions are
+currently implemented using this capability.
+
+Log reducer
+-----------
+
+ACPICA subsystem provides debugging outputs when CONFIG_ACPI_DEBUG is
+enabled. The debugging messages which are deployed via
+ACPI_DEBUG_PRINT() macro can be reduced at 2 levels - per-component
+level (known as debug layer, configured via
+/sys/module/acpi/parameters/debug_layer) and per-type level (known as
+debug level, configured via /sys/module/acpi/parameters/debug_level).
+
+But when the particular layer/level is applied to the control method
+evaluations, the quantity of the debugging outputs may still be too
+large to be put into the kernel log buffer. The idea thus is worked out
+to only enable the particular debug layer/level (normally more detailed)
+logs when the control method evaluation is started, and disable the
+detailed logging when the control method evaluation is stopped.
+
+The following command examples illustrate the usage of the "log reducer"
+functionality:
+
+a. Filter out the debug layer/level matched logs when control methods
+   are being evaluated::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0xXXXXXXXX" > trace_debug_layer
+      # echo "0xYYYYYYYY" > trace_debug_level
+      # echo "enable" > trace_state
+
+b. Filter out the debug layer/level matched logs when the specified
+   control method is being evaluated::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0xXXXXXXXX" > trace_debug_layer
+      # echo "0xYYYYYYYY" > trace_debug_level
+      # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
+      # echo "method" > /sys/module/acpi/parameters/trace_state
+
+c. Filter out the debug layer/level matched logs when the specified
+   control method is being evaluated for the first time::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0xXXXXXXXX" > trace_debug_layer
+      # echo "0xYYYYYYYY" > trace_debug_level
+      # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
+      # echo "method-once" > /sys/module/acpi/parameters/trace_state
+
+Where:
+   0xXXXXXXXX/0xYYYYYYYY
+     Refer to Documentation/firmware-guide/acpi/debug.rst for possible debug layer/level
+     masking values.
+   \PPPP.AAAA.TTTT.HHHH
+     Full path of a control method that can be found in the ACPI namespace.
+     It needn't be an entry of a control method evaluation.
+
+AML tracer
+----------
+
+There are special log entries added by the method tracing facility at
+the "trace points" the AML interpreter starts/stops to execute a control
+method, or an AML opcode. Note that the format of the log entries are
+subject to change::
+
+   [    0.186427]   exdebug-0398 ex_trace_point        : Method Begin [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution.
+   [    0.186630]   exdebug-0398 ex_trace_point        : Opcode Begin [0xf5905c88:If] execution.
+   [    0.186820]   exdebug-0398 ex_trace_point        : Opcode Begin [0xf5905cc0:LEqual] execution.
+   [    0.187010]   exdebug-0398 ex_trace_point        : Opcode Begin [0xf5905a20:-NamePath-] execution.
+   [    0.187214]   exdebug-0398 ex_trace_point        : Opcode End [0xf5905a20:-NamePath-] execution.
+   [    0.187407]   exdebug-0398 ex_trace_point        : Opcode Begin [0xf5905f60:One] execution.
+   [    0.187594]   exdebug-0398 ex_trace_point        : Opcode End [0xf5905f60:One] execution.
+   [    0.187789]   exdebug-0398 ex_trace_point        : Opcode End [0xf5905cc0:LEqual] execution.
+   [    0.187980]   exdebug-0398 ex_trace_point        : Opcode Begin [0xf5905cc0:Return] execution.
+   [    0.188146]   exdebug-0398 ex_trace_point        : Opcode Begin [0xf5905f60:One] execution.
+   [    0.188334]   exdebug-0398 ex_trace_point        : Opcode End [0xf5905f60:One] execution.
+   [    0.188524]   exdebug-0398 ex_trace_point        : Opcode End [0xf5905cc0:Return] execution.
+   [    0.188712]   exdebug-0398 ex_trace_point        : Opcode End [0xf5905c88:If] execution.
+   [    0.188903]   exdebug-0398 ex_trace_point        : Method End [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution.
+
+Developers can utilize these special log entries to track the AML
+interpretation, thus can aid issue debugging and performance tuning. Note
+that, as the "AML tracer" logs are implemented via ACPI_DEBUG_PRINT()
+macro, CONFIG_ACPI_DEBUG is also required to be enabled for enabling
+"AML tracer" logs.
+
+The following command examples illustrate the usage of the "AML tracer"
+functionality:
+
+a. Filter out the method start/stop "AML tracer" logs when control
+   methods are being evaluated::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0x80" > trace_debug_layer
+      # echo "0x10" > trace_debug_level
+      # echo "enable" > trace_state
+
+b. Filter out the method start/stop "AML tracer" when the specified
+   control method is being evaluated::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0x80" > trace_debug_layer
+      # echo "0x10" > trace_debug_level
+      # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
+      # echo "method" > trace_state
+
+c. Filter out the method start/stop "AML tracer" logs when the specified
+   control method is being evaluated for the first time::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0x80" > trace_debug_layer
+      # echo "0x10" > trace_debug_level
+      # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
+      # echo "method-once" > trace_state
+
+d. Filter out the method/opcode start/stop "AML tracer" when the
+   specified control method is being evaluated::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0x80" > trace_debug_layer
+      # echo "0x10" > trace_debug_level
+      # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
+      # echo "opcode" > trace_state
+
+e. Filter out the method/opcode start/stop "AML tracer" when the
+   specified control method is being evaluated for the first time::
+
+      # cd /sys/module/acpi/parameters
+      # echo "0x80" > trace_debug_layer
+      # echo "0x10" > trace_debug_level
+      # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
+      # echo "opcode-opcode" > trace_state
+
+Note that all above method tracing facility related module parameters can
+be used as the boot parameters, for example::
+
+   acpi.trace_debug_layer=0x80 acpi.trace_debug_level=0x10 \
+   acpi.trace_method_name=\_SB.LID0._LID acpi.trace_state=opcode-once
+
+
+Interface descriptions
+======================
+
+All method tracing functions can be configured via ACPI module
+parameters that are accessible at /sys/module/acpi/parameters/:
+
+trace_method_name
+  The full path of the AML method that the user wants to trace.
+
+  Note that the full path shouldn't contain the trailing "_"s in its
+  name segments but may contain "\" to form an absolute path.
+
+trace_debug_layer
+  The temporary debug_layer used when the tracing feature is enabled.
+
+  Using ACPI_EXECUTER (0x80) by default, which is the debug_layer
+  used to match all "AML tracer" logs.
+
+trace_debug_level
+  The temporary debug_level used when the tracing feature is enabled.
+
+  Using ACPI_LV_TRACE_POINT (0x10) by default, which is the
+  debug_level used to match all "AML tracer" logs.
+
+trace_state
+  The status of the tracing feature.
+
+  Users can enable/disable this debug tracing feature by executing
+  the following command::
+
+   # echo string > /sys/module/acpi/parameters/trace_state
+
+Where "string" should be one of the following:
+
+"disable"
+  Disable the method tracing feature.
+
+"enable"
+  Enable the method tracing feature.
+  
+  ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
+  during any method execution will be logged.
+
+"method"
+  Enable the method tracing feature.
+
+  ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
+  during method execution of "trace_method_name" will be logged.
+
+"method-once"
+  Enable the method tracing feature.
+
+  ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
+  during method execution of "trace_method_name" will be logged only once.
+
+"opcode"
+  Enable the method tracing feature.
+
+  ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
+  during method/opcode execution of "trace_method_name" will be logged.
+
+"opcode-once"
+  Enable the method tracing feature.
+
+  ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
+  during method/opcode execution of "trace_method_name" will be logged only
+  once.
+
+Note that, the difference between the "enable" and other feature
+enabling options are:
+
+1. When "enable" is specified, since
+   "trace_debug_layer/trace_debug_level" shall apply to all control
+   method evaluations, after configuring "trace_state" to "enable",
+   "trace_method_name" will be reset to NULL.
+2. When "method/opcode" is specified, if
+   "trace_method_name" is NULL when "trace_state" is configured to
+   these options, the "trace_debug_layer/trace_debug_level" will
+   apply to all control method evaluations.