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, 100 insertions, 0 deletions

diff --git a/Documentation/admin-guide/media/technisat.rst b/Documentation/admin-guide/media/technisat.rst
new file mode 100644
index 000000000..9eaa12366
--- /dev/null
+++ b/Documentation/admin-guide/media/technisat.rst
@@ -0,0 +1,100 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+How to set up the Technisat/B2C2 Flexcop devices
+================================================
+
+.. note::
+
+   This documentation is outdated.
+
+Author: Uwe Bugla <uwe.bugla@gmx.de> August 2009
+
+Find out what device you have
+-----------------------------
+
+Important Notice: The driver does NOT support Technisat USB 2 devices!
+
+First start your linux box with a shipped kernel:
+
+.. code-block:: none
+
+	lspci -vvv for a PCI device (lsusb -vvv for an USB device) will show you for example:
+	02:0b.0 Network controller: Techsan Electronics Co Ltd B2C2 FlexCopII DVB chip /
+	Technisat SkyStar2 DVB card (rev 02)
+
+	dmesg | grep frontend may show you for example:
+	DVB: registering frontend 0 (Conexant CX24123/CX24109)...
+
+Kernel compilation:
+-------------------
+
+If the Flexcop / Technisat is the only DVB / TV / Radio device in your box
+get rid of unnecessary modules and check this one:
+
+``Multimedia support`` => ``Customise analog and hybrid tuner modules to build``
+
+In this directory uncheck every driver which is activated there
+(except ``Simple tuner support`` for ATSC 3rd generation only -> see case 9 please).
+
+Then please activate:
+
+- Main module part:
+
+  ``Multimedia support`` => ``DVB/ATSC adapters`` => ``Technisat/B2C2 FlexcopII(b) and FlexCopIII adapters``
+
+  #) => ``Technisat/B2C2 Air/Sky/Cable2PC PCI`` (PCI card) or
+  #) => ``Technisat/B2C2 Air/Sky/Cable2PC USB`` (USB 1.1 adapter)
+     and for troubleshooting purposes:
+  #) => ``Enable debug for the B2C2 FlexCop drivers``
+
+- Frontend / Tuner / Demodulator module part:
+
+  ``Multimedia support`` => ``DVB/ATSC adapters``
+   => ``Customise the frontend modules to build`` ``Customise DVB frontends`` =>
+
+  - SkyStar DVB-S Revision 2.3:
+
+    #) => ``Zarlink VP310/MT312/ZL10313 based``
+    #) => ``Generic I2C PLL based tuners``
+
+  - SkyStar DVB-S Revision 2.6:
+
+    #) => ``ST STV0299 based``
+    #) => ``Generic I2C PLL based tuners``
+
+  - SkyStar DVB-S Revision 2.7:
+
+    #) => ``Samsung S5H1420 based``
+    #) => ``Integrant ITD1000 Zero IF tuner for DVB-S/DSS``
+    #) => ``ISL6421 SEC controller``
+
+  - SkyStar DVB-S Revision 2.8:
+
+    #) => ``Conexant CX24123 based``
+    #) => ``Conexant CX24113/CX24128 tuner for DVB-S/DSS``
+    #) => ``ISL6421 SEC controller``
+
+  - AirStar DVB-T card:
+
+    #) => ``Zarlink MT352 based``
+    #) => ``Generic I2C PLL based tuners``
+
+  - CableStar DVB-C card:
+
+    #) => ``ST STV0297 based``
+    #) => ``Generic I2C PLL based tuners``
+
+  - AirStar ATSC card 1st generation:
+
+    #) => ``Broadcom BCM3510``
+
+  - AirStar ATSC card 2nd generation:
+
+    #) => ``NxtWave Communications NXT2002/NXT2004 based``
+    #) => ``Generic I2C PLL based tuners``
+
+  - AirStar ATSC card 3rd generation:
+
+    #) => ``LG Electronics LGDT3302/LGDT3303 based``
+    #) ``Multimedia support`` => ``Customise analog and hybrid tuner modules to build`` => ``Simple tuner support``
+