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, 137 insertions, 0 deletions

diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
new file mode 100644
index 000000000..82f600093
--- /dev/null
+++ b/drivers/hwmon/occ/common.h
@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/* Copyright IBM Corp 2019 */
+
+#ifndef OCC_COMMON_H
+#define OCC_COMMON_H
+
+#include <linux/hwmon-sysfs.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+
+struct device;
+
+#define OCC_RESP_DATA_BYTES		4089
+
+/*
+ * Same response format for all OCC versions.
+ * Allocate the largest possible response.
+ */
+struct occ_response {
+	u8 seq_no;
+	u8 cmd_type;
+	u8 return_status;
+	__be16 data_length;
+	u8 data[OCC_RESP_DATA_BYTES];
+	__be16 checksum;
+} __packed;
+
+struct occ_sensor_data_block_header {
+	u8 eye_catcher[4];
+	u8 reserved;
+	u8 sensor_format;
+	u8 sensor_length;
+	u8 num_sensors;
+} __packed;
+
+struct occ_sensor_data_block {
+	struct occ_sensor_data_block_header header;
+	u32 data;
+} __packed;
+
+struct occ_poll_response_header {
+	u8 status;
+	u8 ext_status;
+	u8 occs_present;
+	u8 config_data;
+	u8 occ_state;
+	u8 mode;
+	u8 ips_status;
+	u8 error_log_id;
+	__be32 error_log_start_address;
+	__be16 error_log_length;
+	u16 reserved;
+	u8 occ_code_level[16];
+	u8 eye_catcher[6];
+	u8 num_sensor_data_blocks;
+	u8 sensor_data_block_header_version;
+} __packed;
+
+struct occ_poll_response {
+	struct occ_poll_response_header header;
+	struct occ_sensor_data_block block;
+} __packed;
+
+struct occ_sensor {
+	u8 num_sensors;
+	u8 version;
+	void *data;	/* pointer to sensor data start within response */
+};
+
+/*
+ * OCC only provides one sensor data block of each type, but any number of
+ * sensors within that block.
+ */
+struct occ_sensors {
+	struct occ_sensor temp;
+	struct occ_sensor freq;
+	struct occ_sensor power;
+	struct occ_sensor caps;
+	struct occ_sensor extended;
+};
+
+/*
+ * Use our own attribute struct so we can dynamically allocate space for the
+ * name.
+ */
+struct occ_attribute {
+	char name[32];
+	struct sensor_device_attribute_2 sensor;
+};
+
+struct occ {
+	struct device *bus_dev;
+
+	struct occ_response resp;
+	struct occ_sensors sensors;
+
+	int powr_sample_time_us;	/* average power sample time */
+	u8 poll_cmd_data;		/* to perform OCC poll command */
+	int (*send_cmd)(struct occ *occ, u8 *cmd, size_t len, void *resp,
+			size_t resp_len);
+
+	unsigned long next_update;
+	struct mutex lock;		/* lock OCC access */
+	struct mutex hwmon_lock;		/* serialize hwmon registration/removal */
+
+	struct device *hwmon;
+	struct occ_attribute *attrs;
+	struct attribute_group group;
+	const struct attribute_group *groups[2];
+
+	bool active;
+	int error;                      /* final transfer error after retry */
+	int last_error;			/* latest transfer error */
+	unsigned int error_count;       /* number of xfr errors observed */
+	unsigned long last_safe;        /* time OCC entered "safe" state */
+
+	/*
+	 * Store the previous state data for comparison in order to notify
+	 * sysfs readers of state changes.
+	 */
+	int prev_error;
+	u8 prev_stat;
+	u8 prev_ext_stat;
+	u8 prev_occs_present;
+	u8 prev_ips_status;
+	u8 prev_mode;
+};
+
+int occ_active(struct occ *occ, bool active);
+int occ_setup(struct occ *occ);
+int occ_setup_sysfs(struct occ *occ);
+void occ_shutdown(struct occ *occ);
+void occ_shutdown_sysfs(struct occ *occ);
+void occ_sysfs_poll_done(struct occ *occ);
+int occ_update_response(struct occ *occ);
+
+#endif /* OCC_COMMON_H */