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Date: Wed, 11 Nov 2020 08:23:24 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
Valentin Schneider <valentin.schneider@....com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] stop_machine: Add function and caller debug info
The following commit has been merged into the sched/core branch of tip:
Commit-ID: a8b62fd0850503cf1e557d7e5a98d3f1f5c25eef
Gitweb: https://git.kernel.org/tip/a8b62fd0850503cf1e557d7e5a98d3f1f5c25eef
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Mon, 21 Sep 2020 12:58:17 +02:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 10 Nov 2020 18:38:57 +01:00
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: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@....com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Link: https://lkml.kernel.org/r/20201023102346.116513635@infradead.org
---
include/linux/stop_machine.h | 5 +++++
kernel/sched/core.c | 1 +
kernel/stop_machine.c | 27 ++++++++++++++++++++++++---
lib/dump_stack.c | 2 ++
4 files changed, 32 insertions(+), 3 deletions(-)
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 76d8b09..30577c3 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -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 */
/*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7..5e24104 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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);
}
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 865bb02..3cf567c 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -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 @@ repeat:
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 @@ repeat:
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;
diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index a00ee6e..f5a33b6 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -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);
}
/**
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