[PATCH tip/core/rcu 0/6] Miscellaneous fixes for v5.12

[PATCH tip/core/rcu 0/6] Miscellaneous fixes for v5.12

[Paul E. McKenney]

Hello!

This series contains miscellaneous fixes.

1.	Allow try_invoke_on_locked_down_task() with irqs disabled,
	courtesy of Peter Zijlstra.

2.	Remove duplicate include of percpu-rwsem.h, courtesy of Wang Qing.

3.	Add lockdep_assert_irqs_disabled() to rcu_sched_clock_irq()
	and callees.

4.	Add lockdep_assert_irqs_disabled() to raw_spin_unlock_rcu_node()
	macros.

5.	rcu-tasks: Add RCU-tasks self tests, courtesy of Uladzislau Rezki.

6.	Make TASKS_TRACE_RCU select IRQ_WORK.

						Thanx, Paul

------------------------------------------------------------------------

 locking/locktorture.c |    1 
 rcu/Kconfig           |    1 
 rcu/rcu.h             |   16 ++++++++--
 rcu/tasks.h           |   79 ++++++++++++++++++++++++++++++++++++++++++++++++++
 rcu/tree.c            |    4 ++
 rcu/tree_plugin.h     |    1 
 rcu/tree_stall.h      |    8 +++++
 sched/core.c          |    9 ++---
 8 files changed, 110 insertions(+), 9 deletions(-)

[PATCH tip/core/rcu 1/6] sched/core: Allow try_invoke_on_locked_down_task() with irqs disabled

[paulmck]

From: Peter Zijlstra <peterz@infradead.org>

The try_invoke_on_locked_down_task() function currently requires
that interrupts be enabled, but it is called with interrupts
disabled from rcu_print_task_stall(), resulting in an "IRQs not
enabled as expected" diagnostic.  This commit therefore updates
try_invoke_on_locked_down_task() to use raw_spin_lock_irqsave() instead
of raw_spin_lock_irq(), thus allowing use from either context.

Link: https://lore.kernel.org/lkml/000000000000903d5805ab908fc4@google.com/
Link: https://lore.kernel.org/lkml/20200928075729.GC2611@hirez.programming.kicks-ass.net/
Reported-by: syzbot+cb3b69ae80afd6535b0e@syzkaller.appspotmail.com
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/sched/core.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e7e4534..f768bb0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2989,7 +2989,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 
 /**
  * try_invoke_on_locked_down_task - Invoke a function on task in fixed state
- * @p: Process for which the function is to be invoked.
+ * @p: Process for which the function is to be invoked, can be @current.
  * @func: Function to invoke.
  * @arg: Argument to function.
  *
@@ -3007,12 +3007,11 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
  */
 bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
 {
-	bool ret = false;
 	struct rq_flags rf;
+	bool ret = false;
 	struct rq *rq;
 
-	lockdep_assert_irqs_enabled();
-	raw_spin_lock_irq(&p->pi_lock);
+	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
 	if (p->on_rq) {
 		rq = __task_rq_lock(p, &rf);
 		if (task_rq(p) == rq)
@@ -3029,7 +3028,7 @@ bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct t
 				ret = func(p, arg);
 		}
 	}
-	raw_spin_unlock_irq(&p->pi_lock);
+	raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
 	return ret;
 }
 
-- 
2.9.5

[PATCH tip/core/rcu 2/6] locking: Remove duplicate include of percpu-rwsem.h

[paulmck]

From: Wang Qing <wangqing@vivo.com>

This commit removes an unnecessary #include.

Signed-off-by: Wang Qing <wangqing@vivo.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/locking/locktorture.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 62d215b..af99e9c 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -27,7 +27,6 @@
 #include <linux/moduleparam.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
-#include <linux/percpu-rwsem.h>
 #include <linux/torture.h>
 
 MODULE_LICENSE("GPL");
-- 
2.9.5

[PATCH tip/core/rcu 3/6] rcu: Add lockdep_assert_irqs_disabled() to rcu_sched_clock_irq() and callees

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds a number of lockdep_assert_irqs_disabled() calls
to rcu_sched_clock_irq() and a number of the functions that it calls.
The point of this is to help track down a situation where lockdep appears
to be insisting that interrupts are enabled within these functions, which
should only ever be invoked from the scheduling-clock interrupt handler.

Link: https://lore.kernel.org/lkml/20201111133813.GA81547@elver.google.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree.c        | 4 ++++
 kernel/rcu/tree_plugin.h | 1 +
 kernel/rcu/tree_stall.h  | 8 ++++++++
 3 files changed, 13 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index bd04b09..f70634f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2553,6 +2553,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
 void rcu_sched_clock_irq(int user)
 {
 	trace_rcu_utilization(TPS("Start scheduler-tick"));
+	lockdep_assert_irqs_disabled();
 	raw_cpu_inc(rcu_data.ticks_this_gp);
 	/* The load-acquire pairs with the store-release setting to true. */
 	if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
@@ -2566,6 +2567,7 @@ void rcu_sched_clock_irq(int user)
 	rcu_flavor_sched_clock_irq(user);
 	if (rcu_pending(user))
 		invoke_rcu_core();
+	lockdep_assert_irqs_disabled();
 
 	trace_rcu_utilization(TPS("End scheduler-tick"));
 }
@@ -3690,6 +3692,8 @@ static int rcu_pending(int user)
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 	struct rcu_node *rnp = rdp->mynode;
 
+	lockdep_assert_irqs_disabled();
+
 	/* Check for CPU stalls, if enabled. */
 	check_cpu_stall(rdp);
 
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index fd8a52e..cb76e70 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -682,6 +682,7 @@ static void rcu_flavor_sched_clock_irq(int user)
 {
 	struct task_struct *t = current;
 
+	lockdep_assert_irqs_disabled();
 	if (user || rcu_is_cpu_rrupt_from_idle()) {
 		rcu_note_voluntary_context_switch(current);
 	}
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index ca21d28..4024dcc 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -260,6 +260,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
 	struct task_struct *t;
 	struct task_struct *ts[8];
 
+	lockdep_assert_irqs_disabled();
 	if (!rcu_preempt_blocked_readers_cgp(rnp))
 		return 0;
 	pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
@@ -284,6 +285,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
 				".q"[rscr.rs.b.need_qs],
 				".e"[rscr.rs.b.exp_hint],
 				".l"[rscr.on_blkd_list]);
+		lockdep_assert_irqs_disabled();
 		put_task_struct(t);
 		ndetected++;
 	}
@@ -472,6 +474,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
 	struct rcu_node *rnp;
 	long totqlen = 0;
 
+	lockdep_assert_irqs_disabled();
+
 	/* Kick and suppress, if so configured. */
 	rcu_stall_kick_kthreads();
 	if (rcu_stall_is_suppressed())
@@ -493,6 +497,7 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
 				}
 		}
 		ndetected += rcu_print_task_stall(rnp, flags); // Releases rnp->lock.
+		lockdep_assert_irqs_disabled();
 	}
 
 	for_each_possible_cpu(cpu)
@@ -538,6 +543,8 @@ static void print_cpu_stall(unsigned long gps)
 	struct rcu_node *rnp = rcu_get_root();
 	long totqlen = 0;
 
+	lockdep_assert_irqs_disabled();
+
 	/* Kick and suppress, if so configured. */
 	rcu_stall_kick_kthreads();
 	if (rcu_stall_is_suppressed())
@@ -592,6 +599,7 @@ static void check_cpu_stall(struct rcu_data *rdp)
 	unsigned long js;
 	struct rcu_node *rnp;
 
+	lockdep_assert_irqs_disabled();
 	if ((rcu_stall_is_suppressed() && !READ_ONCE(rcu_kick_kthreads)) ||
 	    !rcu_gp_in_progress())
 		return;
-- 
2.9.5

[PATCH tip/core/rcu 4/6] rcu: Add lockdep_assert_irqs_disabled() to raw_spin_unlock_rcu_node() macros

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds a lockdep_assert_irqs_disabled() call to the
helper macros that release the rcu_node structure's ->lock, namely
to raw_spin_unlock_rcu_node(), raw_spin_unlock_irq_rcu_node() and
raw_spin_unlock_irqrestore_rcu_node().  The point of this is to help track
down a situation where lockdep appears to be insisting that interrupts
are enabled while holding an rcu_node structure's ->lock.

Link: https://lore.kernel.org/lkml/20201111133813.GA81547@elver.google.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcu.h | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index e01cba5..839f5be 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -378,7 +378,11 @@ do {									\
 	smp_mb__after_unlock_lock();					\
 } while (0)
 
-#define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock))
+#define raw_spin_unlock_rcu_node(p)					\
+do {									\
+	lockdep_assert_irqs_disabled();					\
+	raw_spin_unlock(&ACCESS_PRIVATE(p, lock));			\
+} while (0)
 
 #define raw_spin_lock_irq_rcu_node(p)					\
 do {									\
@@ -387,7 +391,10 @@ do {									\
 } while (0)
 
 #define raw_spin_unlock_irq_rcu_node(p)					\
-	raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock))
+do {									\
+	lockdep_assert_irqs_disabled();					\
+	raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock));			\
+} while (0)
 
 #define raw_spin_lock_irqsave_rcu_node(p, flags)			\
 do {									\
@@ -396,7 +403,10 @@ do {									\
 } while (0)
 
 #define raw_spin_unlock_irqrestore_rcu_node(p, flags)			\
-	raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)
+do {									\
+	lockdep_assert_irqs_disabled();					\
+	raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags);	\
+} while (0)
 
 #define raw_spin_trylock_rcu_node(p)					\
 ({									\
-- 
2.9.5

[PATCH tip/core/rcu 5/6] rcu-tasks: Add RCU-tasks self tests

[paulmck]

From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>

This commit adds self tests for early-boot use of RCU-tasks grace periods.
It tests all three variants (Rude, Tasks, and Tasks Trace) and covers
both synchronous (e.g., synchronize_rcu_tasks()) and asynchronous (e.g.,
call_rcu_tasks()) grace-period APIs.

Self-tests are run only in kernels built with CONFIG_PROVE_RCU=y.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
[ paulmck: Handle CONFIG_PROVE_RCU=n and identify test cases' callbacks. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tasks.h | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 73bbe79..74767d3 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1231,6 +1231,82 @@ void show_rcu_tasks_gp_kthreads(void)
 }
 #endif /* #ifndef CONFIG_TINY_RCU */
 
+#ifdef CONFIG_PROVE_RCU
+struct rcu_tasks_test_desc {
+	struct rcu_head rh;
+	const char *name;
+	bool notrun;
+};
+
+static struct rcu_tasks_test_desc tests[] = {
+	{
+		.name = "call_rcu_tasks()",
+		/* If not defined, the test is skipped. */
+		.notrun = !IS_ENABLED(CONFIG_TASKS_RCU),
+	},
+	{
+		.name = "call_rcu_tasks_rude()",
+		/* If not defined, the test is skipped. */
+		.notrun = !IS_ENABLED(CONFIG_TASKS_RUDE_RCU),
+	},
+	{
+		.name = "call_rcu_tasks_trace()",
+		/* If not defined, the test is skipped. */
+		.notrun = !IS_ENABLED(CONFIG_TASKS_TRACE_RCU)
+	}
+};
+
+static void test_rcu_tasks_callback(struct rcu_head *rhp)
+{
+	struct rcu_tasks_test_desc *rttd =
+		container_of(rhp, struct rcu_tasks_test_desc, rh);
+
+	pr_info("Callback from %s invoked.\n", rttd->name);
+
+	rttd->notrun = true;
+}
+
+static void rcu_tasks_initiate_self_tests(void)
+{
+	pr_info("Running RCU-tasks wait API self tests\n");
+#ifdef CONFIG_TASKS_RCU
+	synchronize_rcu_tasks();
+	call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
+#endif
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+	synchronize_rcu_tasks_rude();
+	call_rcu_tasks_rude(&tests[1].rh, test_rcu_tasks_callback);
+#endif
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+	synchronize_rcu_tasks_trace();
+	call_rcu_tasks_trace(&tests[2].rh, test_rcu_tasks_callback);
+#endif
+}
+
+static int rcu_tasks_verify_self_tests(void)
+{
+	int ret = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
+		if (!tests[i].notrun) {		// still hanging.
+			pr_err("%s has been failed.\n", tests[i].name);
+			ret = -1;
+		}
+	}
+
+	if (ret)
+		WARN_ON(1);
+
+	return ret;
+}
+late_initcall(rcu_tasks_verify_self_tests);
+#else /* #ifdef CONFIG_PROVE_RCU */
+static void rcu_tasks_initiate_self_tests(void) { }
+#endif /* #else #ifdef CONFIG_PROVE_RCU */
+
 void __init rcu_init_tasks_generic(void)
 {
 #ifdef CONFIG_TASKS_RCU
@@ -1244,6 +1320,9 @@ void __init rcu_init_tasks_generic(void)
 #ifdef CONFIG_TASKS_TRACE_RCU
 	rcu_spawn_tasks_trace_kthread();
 #endif
+
+	// Run the self-tests.
+	rcu_tasks_initiate_self_tests();
 }
 
 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
-- 
2.9.5

[PATCH tip/core/rcu 6/6] rcu: Make TASKS_TRACE_RCU select IRQ_WORK

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

Tasks Trace RCU uses irq_work_queue() to safely awaken its grace-period
kthread, so this commit therefore causes the TASKS_TRACE_RCU Kconfig
option select the IRQ_WORK Kconfig option.

Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index b71e21f..84dfa8d 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -95,6 +95,7 @@ config TASKS_RUDE_RCU
 
 config TASKS_TRACE_RCU
 	def_bool 0
+	select IRQ_WORK
 	help
 	  This option enables a task-based RCU implementation that uses
 	  explicit rcu_read_lock_trace() read-side markers, and allows
-- 
2.9.5