Commit a8b62fd0 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

stop_machine: Add function and caller debug info 



Crashes in stop-machine are hard to connect to the calling code, add a
little something to help with that.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Reviewed-by: default avatarDaniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lkml.kernel.org/r/20201023102346.116513635@infradead.org
parent 23859ae4

include/linux/stop_machine.h

+5 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ typedef int (*cpu_stop_fn_t)(void *arg); 
struct cpu_stop_work {

	struct list_head	list;		/* cpu_stopper->works */

	cpu_stop_fn_t		fn;

	unsigned long		caller;

	void			*arg;

	struct cpu_stop_done	*done;

};
@@ -36,6 +37,8 @@ void stop_machine_park(int cpu); 
void stop_machine_unpark(int cpu);

void stop_machine_yield(const struct cpumask *cpumask);



extern void print_stop_info(const char *log_lvl, struct task_struct *task);



#else	/* CONFIG_SMP */



#include <linux/workqueue.h>
@@ -80,6 +83,8 @@ static inline bool stop_one_cpu_nowait(unsigned int cpu, 
	return false;

}



static inline void print_stop_info(const char *log_lvl, struct task_struct *task) { }



#endif	/* CONFIG_SMP */



/*

kernel/sched/core.c

+1 −0
Original line number Diff line number Diff line
@@ -6447,6 +6447,7 @@ void sched_show_task(struct task_struct *p) 
		(unsigned long)task_thread_info(p)->flags);



	print_worker_info(KERN_INFO, p);

	print_stop_info(KERN_INFO, p);

	show_stack(p, NULL, KERN_INFO);

	put_task_stack(p);

}

kernel/stop_machine.c

+24 −3
Original line number Diff line number Diff line
@@ -42,11 +42,27 @@ struct cpu_stopper { 
	struct list_head	works;		/* list of pending works */



	struct cpu_stop_work	stop_work;	/* for stop_cpus */

	unsigned long		caller;

	cpu_stop_fn_t		fn;

};



static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);

static bool stop_machine_initialized = false;



void print_stop_info(const char *log_lvl, struct task_struct *task)

{

	/*

	 * If @task is a stopper task, it cannot migrate and task_cpu() is

	 * stable.

	 */

	struct cpu_stopper *stopper = per_cpu_ptr(&cpu_stopper, task_cpu(task));



	if (task != stopper->thread)

		return;



	printk("%sStopper: %pS <- %pS\n", log_lvl, stopper->fn, (void *)stopper->caller);

}



/* static data for stop_cpus */

static DEFINE_MUTEX(stop_cpus_mutex);

static bool stop_cpus_in_progress;
@@ -123,7 +139,7 @@ static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) 
int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)

{

	struct cpu_stop_done done;

	struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };

	struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done, .caller = _RET_IP_ };



	cpu_stop_init_done(&done, 1);

	if (!cpu_stop_queue_work(cpu, &work))
@@ -331,7 +347,8 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * 
	work1 = work2 = (struct cpu_stop_work){

		.fn = multi_cpu_stop,

		.arg = &msdata,

		.done = &done

		.done = &done,

		.caller = _RET_IP_,

	};



	cpu_stop_init_done(&done, 2);
@@ -367,7 +384,7 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * 
bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,

			struct cpu_stop_work *work_buf)

{

	*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };

	*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, .caller = _RET_IP_, };

	return cpu_stop_queue_work(cpu, work_buf);

}
@@ -487,6 +504,8 @@ static void cpu_stopper_thread(unsigned int cpu) 
		int ret;



		/* cpu stop callbacks must not sleep, make in_atomic() == T */

		stopper->caller = work->caller;

		stopper->fn = fn;

		preempt_count_inc();

		ret = fn(arg);

		if (done) {
@@ -495,6 +514,8 @@ static void cpu_stopper_thread(unsigned int cpu) 
			cpu_stop_signal_done(done);

		}

		preempt_count_dec();

		stopper->fn = NULL;

		stopper->caller = 0;

		WARN_ONCE(preempt_count(),

			  "cpu_stop: %ps(%p) leaked preempt count\n", fn, arg);

		goto repeat;

lib/dump_stack.c

+2 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/atomic.h>

#include <linux/kexec.h>

#include <linux/utsname.h>

#include <linux/stop_machine.h>



static char dump_stack_arch_desc_str[128];
@@ -57,6 +58,7 @@ void dump_stack_print_info(const char *log_lvl) 
		       log_lvl, dump_stack_arch_desc_str);



	print_worker_info(log_lvl, current);

	print_stop_info(log_lvl, current);

}



/**