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3bd3706251
In commit:
4b53a3412d ("sched/core: Remove the tsk_nr_cpus_allowed() wrapper")
the tsk_nr_cpus_allowed() wrapper was removed. There was not
much difference in !RT but in RT we used this to implement
migrate_disable(). Within a migrate_disable() section the CPU mask is
restricted to single CPU while the "normal" CPU mask remains untouched.
As an alternative implementation Ingo suggested to use:
struct task_struct {
const cpumask_t *cpus_ptr;
cpumask_t cpus_mask;
};
with
t->cpus_ptr = &t->cpus_mask;
In -RT we then can switch the cpus_ptr to:
t->cpus_ptr = &cpumask_of(task_cpu(p));
in a migration disabled region. The rules are simple:
- Code that 'uses' ->cpus_allowed would use the pointer.
- Code that 'modifies' ->cpus_allowed would use the direct mask.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190423142636.14347-1-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
140 lines
2.9 KiB
C
140 lines
2.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/module.h>
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#include <linux/kthread.h>
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/*
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* Any file that uses trace points, must include the header.
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* But only one file, must include the header by defining
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* CREATE_TRACE_POINTS first. This will make the C code that
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* creates the handles for the trace points.
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*/
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#define CREATE_TRACE_POINTS
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#include "trace-events-sample.h"
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static const char *random_strings[] = {
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"Mother Goose",
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"Snoopy",
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"Gandalf",
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"Frodo",
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"One ring to rule them all"
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};
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static void simple_thread_func(int cnt)
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{
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int array[6];
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int len = cnt % 5;
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int i;
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set_current_state(TASK_INTERRUPTIBLE);
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schedule_timeout(HZ);
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for (i = 0; i < len; i++)
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array[i] = i + 1;
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array[i] = 0;
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/* Silly tracepoints */
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trace_foo_bar("hello", cnt, array, random_strings[len],
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current->cpus_ptr);
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trace_foo_with_template_simple("HELLO", cnt);
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trace_foo_bar_with_cond("Some times print", cnt);
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trace_foo_with_template_cond("prints other times", cnt);
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trace_foo_with_template_print("I have to be different", cnt);
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}
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static int simple_thread(void *arg)
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{
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int cnt = 0;
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while (!kthread_should_stop())
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simple_thread_func(cnt++);
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return 0;
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}
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static struct task_struct *simple_tsk;
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static struct task_struct *simple_tsk_fn;
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static void simple_thread_func_fn(int cnt)
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{
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set_current_state(TASK_INTERRUPTIBLE);
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schedule_timeout(HZ);
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/* More silly tracepoints */
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trace_foo_bar_with_fn("Look at me", cnt);
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trace_foo_with_template_fn("Look at me too", cnt);
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}
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static int simple_thread_fn(void *arg)
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{
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int cnt = 0;
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while (!kthread_should_stop())
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simple_thread_func_fn(cnt++);
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return 0;
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}
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static DEFINE_MUTEX(thread_mutex);
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static int simple_thread_cnt;
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int foo_bar_reg(void)
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{
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mutex_lock(&thread_mutex);
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if (simple_thread_cnt++)
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goto out;
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pr_info("Starting thread for foo_bar_fn\n");
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/*
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* We shouldn't be able to start a trace when the module is
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* unloading (there's other locks to prevent that). But
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* for consistency sake, we still take the thread_mutex.
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*/
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simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
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out:
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mutex_unlock(&thread_mutex);
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return 0;
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}
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void foo_bar_unreg(void)
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{
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mutex_lock(&thread_mutex);
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if (--simple_thread_cnt)
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goto out;
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pr_info("Killing thread for foo_bar_fn\n");
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if (simple_tsk_fn)
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kthread_stop(simple_tsk_fn);
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simple_tsk_fn = NULL;
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out:
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mutex_unlock(&thread_mutex);
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}
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static int __init trace_event_init(void)
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{
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simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
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if (IS_ERR(simple_tsk))
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return -1;
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return 0;
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}
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static void __exit trace_event_exit(void)
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{
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kthread_stop(simple_tsk);
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mutex_lock(&thread_mutex);
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if (simple_tsk_fn)
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kthread_stop(simple_tsk_fn);
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simple_tsk_fn = NULL;
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mutex_unlock(&thread_mutex);
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}
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module_init(trace_event_init);
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module_exit(trace_event_exit);
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MODULE_AUTHOR("Steven Rostedt");
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MODULE_DESCRIPTION("trace-events-sample");
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MODULE_LICENSE("GPL");
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