From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- drivers/cpuidle/governor.c | 123 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 drivers/cpuidle/governor.c (limited to 'drivers/cpuidle/governor.c') diff --git a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c new file mode 100644 index 000000000..5d0e7f78c --- /dev/null +++ b/drivers/cpuidle/governor.c @@ -0,0 +1,123 @@ +/* + * governor.c - governor support + * + * (C) 2006-2007 Venkatesh Pallipadi + * Shaohua Li + * Adam Belay + * + * This code is licenced under the GPL. + */ + +#include +#include +#include +#include +#include + +#include "cpuidle.h" + +char param_governor[CPUIDLE_NAME_LEN]; + +LIST_HEAD(cpuidle_governors); +struct cpuidle_governor *cpuidle_curr_governor; +struct cpuidle_governor *cpuidle_prev_governor; + +/** + * cpuidle_find_governor - finds a governor of the specified name + * @str: the name + * + * Must be called with cpuidle_lock acquired. + */ +struct cpuidle_governor *cpuidle_find_governor(const char *str) +{ + struct cpuidle_governor *gov; + + list_for_each_entry(gov, &cpuidle_governors, governor_list) + if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN)) + return gov; + + return NULL; +} + +/** + * cpuidle_switch_governor - changes the governor + * @gov: the new target governor + * Must be called with cpuidle_lock acquired. + */ +int cpuidle_switch_governor(struct cpuidle_governor *gov) +{ + struct cpuidle_device *dev; + + if (!gov) + return -EINVAL; + + if (gov == cpuidle_curr_governor) + return 0; + + cpuidle_uninstall_idle_handler(); + + if (cpuidle_curr_governor) { + list_for_each_entry(dev, &cpuidle_detected_devices, device_list) + cpuidle_disable_device(dev); + } + + cpuidle_curr_governor = gov; + + list_for_each_entry(dev, &cpuidle_detected_devices, device_list) + cpuidle_enable_device(dev); + + cpuidle_install_idle_handler(); + pr_info("cpuidle: using governor %s\n", gov->name); + + return 0; +} + +/** + * cpuidle_register_governor - registers a governor + * @gov: the governor + */ +int cpuidle_register_governor(struct cpuidle_governor *gov) +{ + int ret = -EEXIST; + + if (!gov || !gov->select) + return -EINVAL; + + if (cpuidle_disabled()) + return -ENODEV; + + mutex_lock(&cpuidle_lock); + if (cpuidle_find_governor(gov->name) == NULL) { + ret = 0; + list_add_tail(&gov->governor_list, &cpuidle_governors); + if (!cpuidle_curr_governor || + !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) || + (cpuidle_curr_governor->rating < gov->rating && + strncasecmp(param_governor, cpuidle_curr_governor->name, + CPUIDLE_NAME_LEN))) + cpuidle_switch_governor(gov); + } + mutex_unlock(&cpuidle_lock); + + return ret; +} + +/** + * cpuidle_governor_latency_req - Compute a latency constraint for CPU + * @cpu: Target CPU + */ +s64 cpuidle_governor_latency_req(unsigned int cpu) +{ + struct device *device = get_cpu_device(cpu); + int device_req = dev_pm_qos_raw_resume_latency(device); + int global_req = cpu_latency_qos_limit(); + int global_wake_req = cpu_wakeup_latency_qos_limit(); + + if (global_req > global_wake_req) + global_req = global_wake_req; + + if (device_req > global_req) + device_req = global_req; + + return (s64)device_req * NSEC_PER_USEC; +} -- cgit v1.3.1