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/cpufreq/cpufreq_stats.c | 289 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 289 insertions(+) create mode 100644 drivers/cpufreq/cpufreq_stats.c (limited to 'drivers/cpufreq/cpufreq_stats.c') diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c new file mode 100644 index 000000000..670a10c3e --- /dev/null +++ b/drivers/cpufreq/cpufreq_stats.c @@ -0,0 +1,289 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * drivers/cpufreq/cpufreq_stats.c + * + * Copyright (C) 2003-2004 Venkatesh Pallipadi . + * (C) 2004 Zou Nan hai . + */ + +#include +#include +#include +#include +#include + +struct cpufreq_stats { + unsigned int total_trans; + unsigned long long last_time; + unsigned int max_state; + unsigned int state_num; + unsigned int last_index; + u64 *time_in_state; + unsigned int *freq_table; + unsigned int *trans_table; + + /* Deferred reset */ + unsigned int reset_pending; + unsigned long long reset_time; +}; + +static void cpufreq_stats_update(struct cpufreq_stats *stats, + unsigned long long time) +{ + unsigned long long cur_time = local_clock(); + + stats->time_in_state[stats->last_index] += cur_time - time; + stats->last_time = cur_time; +} + +static void cpufreq_stats_reset_table(struct cpufreq_stats *stats) +{ + unsigned int count = stats->max_state; + + memset(stats->time_in_state, 0, count * sizeof(u64)); + memset(stats->trans_table, 0, count * count * sizeof(int)); + stats->last_time = local_clock(); + stats->total_trans = 0; + + /* Adjust for the time elapsed since reset was requested */ + WRITE_ONCE(stats->reset_pending, 0); + /* + * Prevent the reset_time read from being reordered before the + * reset_pending accesses in cpufreq_stats_record_transition(). + */ + smp_rmb(); + cpufreq_stats_update(stats, READ_ONCE(stats->reset_time)); +} + +static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf) +{ + struct cpufreq_stats *stats = policy->stats; + + if (READ_ONCE(stats->reset_pending)) + return sprintf(buf, "%d\n", 0); + else + return sprintf(buf, "%u\n", stats->total_trans); +} +cpufreq_freq_attr_ro(total_trans); + +static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf) +{ + struct cpufreq_stats *stats = policy->stats; + bool pending = READ_ONCE(stats->reset_pending); + unsigned long long time; + ssize_t len = 0; + int i; + + for (i = 0; i < stats->state_num; i++) { + if (pending) { + if (i == stats->last_index) { + /* + * Prevent the reset_time read from occurring + * before the reset_pending read above. + */ + smp_rmb(); + time = local_clock() - READ_ONCE(stats->reset_time); + } else { + time = 0; + } + } else { + time = stats->time_in_state[i]; + if (i == stats->last_index) + time += local_clock() - stats->last_time; + } + + len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i], + nsec_to_clock_t(time)); + } + return len; +} +cpufreq_freq_attr_ro(time_in_state); + +/* We don't care what is written to the attribute */ +static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf, + size_t count) +{ + struct cpufreq_stats *stats = policy->stats; + + /* + * Defer resetting of stats to cpufreq_stats_record_transition() to + * avoid races. + */ + WRITE_ONCE(stats->reset_time, local_clock()); + /* + * The memory barrier below is to prevent the readers of reset_time from + * seeing a stale or partially updated value. + */ + smp_wmb(); + WRITE_ONCE(stats->reset_pending, 1); + + return count; +} +cpufreq_freq_attr_wo(reset); + +static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf) +{ + struct cpufreq_stats *stats = policy->stats; + bool pending = READ_ONCE(stats->reset_pending); + ssize_t len = 0; + int i, j, count; + + len += sysfs_emit_at(buf, len, " From : To\n"); + len += sysfs_emit_at(buf, len, " : "); + for (i = 0; i < stats->state_num; i++) { + if (len >= PAGE_SIZE - 1) + break; + len += sysfs_emit_at(buf, len, "%9u ", stats->freq_table[i]); + } + if (len >= PAGE_SIZE - 1) + return PAGE_SIZE - 1; + + len += sysfs_emit_at(buf, len, "\n"); + + for (i = 0; i < stats->state_num; i++) { + if (len >= PAGE_SIZE - 1) + break; + + len += sysfs_emit_at(buf, len, "%9u: ", stats->freq_table[i]); + + for (j = 0; j < stats->state_num; j++) { + if (len >= PAGE_SIZE - 1) + break; + + if (pending) + count = 0; + else + count = stats->trans_table[i * stats->max_state + j]; + + len += sysfs_emit_at(buf, len, "%9u ", count); + } + if (len >= PAGE_SIZE - 1) + break; + len += sysfs_emit_at(buf, len, "\n"); + } + + if (len >= PAGE_SIZE - 1) { + pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n"); + return -EFBIG; + } + return len; +} +cpufreq_freq_attr_ro(trans_table); + +static struct attribute *default_attrs[] = { + &total_trans.attr, + &time_in_state.attr, + &reset.attr, + &trans_table.attr, + NULL +}; +static const struct attribute_group stats_attr_group = { + .attrs = default_attrs, + .name = "stats" +}; + +static int freq_table_get_index(struct cpufreq_stats *stats, unsigned int freq) +{ + int index; + for (index = 0; index < stats->max_state; index++) + if (stats->freq_table[index] == freq) + return index; + return -1; +} + +void cpufreq_stats_free_table(struct cpufreq_policy *policy) +{ + struct cpufreq_stats *stats = policy->stats; + + /* Already freed */ + if (!stats) + return; + + pr_debug("%s: Free stats table\n", __func__); + + sysfs_remove_group(&policy->kobj, &stats_attr_group); + kfree(stats->time_in_state); + kfree(stats); + policy->stats = NULL; +} + +void cpufreq_stats_create_table(struct cpufreq_policy *policy) +{ + unsigned int i = 0, count; + struct cpufreq_stats *stats; + unsigned int alloc_size; + struct cpufreq_frequency_table *pos; + + count = cpufreq_table_count_valid_entries(policy); + if (!count) + return; + + /* stats already initialized */ + if (policy->stats) + return; + + stats = kzalloc_obj(*stats); + if (!stats) + return; + + alloc_size = count * sizeof(int) + count * sizeof(u64); + + alloc_size += count * count * sizeof(int); + + /* Allocate memory for time_in_state/freq_table/trans_table in one go */ + stats->time_in_state = kzalloc(alloc_size, GFP_KERNEL); + if (!stats->time_in_state) + goto free_stat; + + stats->freq_table = (unsigned int *)(stats->time_in_state + count); + + stats->trans_table = stats->freq_table + count; + + stats->max_state = count; + + /* Find valid-unique entries */ + cpufreq_for_each_valid_entry(pos, policy->freq_table) + if (policy->freq_table_sorted != CPUFREQ_TABLE_UNSORTED || + freq_table_get_index(stats, pos->frequency) == -1) + stats->freq_table[i++] = pos->frequency; + + stats->state_num = i; + stats->last_time = local_clock(); + stats->last_index = freq_table_get_index(stats, policy->cur); + + policy->stats = stats; + if (!sysfs_create_group(&policy->kobj, &stats_attr_group)) + return; + + /* We failed, release resources */ + policy->stats = NULL; + kfree(stats->time_in_state); +free_stat: + kfree(stats); +} + +void cpufreq_stats_record_transition(struct cpufreq_policy *policy, + unsigned int new_freq) +{ + struct cpufreq_stats *stats = policy->stats; + int old_index, new_index; + + if (unlikely(!stats)) + return; + + if (unlikely(READ_ONCE(stats->reset_pending))) + cpufreq_stats_reset_table(stats); + + old_index = stats->last_index; + new_index = freq_table_get_index(stats, new_freq); + + /* We can't do stats->time_in_state[-1]= .. */ + if (unlikely(old_index == -1 || new_index == -1 || old_index == new_index)) + return; + + cpufreq_stats_update(stats, stats->last_time); + + stats->last_index = new_index; + stats->trans_table[old_index * stats->max_state + new_index]++; + stats->total_trans++; +} -- cgit v1.3.1