Merge 5.10.194 into android12-5.10-lts

Changes in 5.10.194
	module: Expose module_init_layout_section()
	arm64: module-plts: inline linux/moduleloader.h
	arm64: module: Use module_init_layout_section() to spot init sections
	ARM: module: Use module_init_layout_section() to spot init sections
	mhi: pci_generic: Fix implicit conversion warning
	Revert "drm/amdgpu: install stub fence into potential unused fence pointers"
	Revert "MIPS: Alchemy: fix dbdma2"
	rcu: Prevent expedited GP from enabling tick on offline CPU
	rcu-tasks: Fix IPI failure handling in trc_wait_for_one_reader
	rcu-tasks: Wait for trc_read_check_handler() IPIs
	rcu-tasks: Add trc_inspect_reader() checks for exiting critical section
	Linux 5.10.194

Change-Id: I1e4230071f3ca3c9e811aeba31446875028d7b3d
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

kernel/module.c

@@ -2297,7 +2297,7 @@ void *__symbol_get(const char *symbol)
 }
 EXPORT_SYMBOL_GPL(__symbol_get);
 
-static bool module_init_layout_section(const char *sname)
+bool module_init_layout_section(const char *sname)
 {
 #ifndef CONFIG_MODULE_UNLOAD
 	if (module_exit_section(sname))

kernel/rcu/tasks.h

@@ -874,7 +874,7 @@ reset_ipi:
 static bool trc_inspect_reader(struct task_struct *t, void *arg)
 {
 	int cpu = task_cpu(t);
-	bool in_qs = false;
+	int nesting;
 	bool ofl = cpu_is_offline(cpu);
 
 	if (task_curr(t)) {
@@ -894,18 +894,18 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
 		n_heavy_reader_updates++;
 		if (ofl)
 			n_heavy_reader_ofl_updates++;
-		in_qs = true;
+		nesting = 0;
 	} else {
 		// The task is not running, so C-language access is safe.
-		in_qs = likely(!t->trc_reader_nesting);
+		nesting = t->trc_reader_nesting;
 	}
 
-	// Mark as checked so that the grace-period kthread will
-	// remove it from the holdout list.
-	t->trc_reader_checked = true;
-
-	if (in_qs)
-		return true;  // Already in quiescent state, done!!!
+	// If not exiting a read-side critical section, mark as checked
+	// so that the grace-period kthread will remove it from the
+	// holdout list.
+	t->trc_reader_checked = nesting >= 0;
+	if (nesting <= 0)
+		return !nesting;  // If in QS, done, otherwise try again later.
 
 	// The task is in a read-side critical section, so set up its
 	// state so that it will awaken the grace-period kthread upon exit
@@ -958,9 +958,11 @@ static void trc_wait_for_one_reader(struct task_struct *t,
 		if (smp_call_function_single(cpu, trc_read_check_handler, t, 0)) {
 			// Just in case there is some other reason for
 			// failure than the target CPU being offline.
+			WARN_ONCE(1, "%s():  smp_call_function_single() failed for CPU: %d\n",
+				  __func__, cpu);
 			rcu_tasks_trace.n_ipis_fails++;
 			per_cpu(trc_ipi_to_cpu, cpu) = false;
-			t->trc_ipi_to_cpu = cpu;
+			t->trc_ipi_to_cpu = -1;
 		}
 	}
 }
@@ -1081,14 +1083,28 @@ static void check_all_holdout_tasks_trace(struct list_head *hop,
 	}
 }
 
+static void rcu_tasks_trace_empty_fn(void *unused)
+{
+}
+
 /* Wait for grace period to complete and provide ordering. */
 static void rcu_tasks_trace_postgp(struct rcu_tasks *rtp)
 {
+	int cpu;
 	bool firstreport;
 	struct task_struct *g, *t;
 	LIST_HEAD(holdouts);
 	long ret;
 
+	// Wait for any lingering IPI handlers to complete.  Note that
+	// if a CPU has gone offline or transitioned to userspace in the
+	// meantime, all IPI handlers should have been drained beforehand.
+	// Yes, this assumes that CPUs process IPIs in order.  If that ever
+	// changes, there will need to be a recheck and/or timed wait.
+	for_each_online_cpu(cpu)
+		if (smp_load_acquire(per_cpu_ptr(&trc_ipi_to_cpu, cpu)))
+			smp_call_function_single(cpu, rcu_tasks_trace_empty_fn, NULL, 1);
+
 	// Remove the safety count.
 	smp_mb__before_atomic();  // Order vs. earlier atomics
 	atomic_dec(&trc_n_readers_need_end);

kernel/rcu/tree_exp.h

@@ -507,7 +507,10 @@ static void synchronize_rcu_expedited_wait(void)
 				if (rdp->rcu_forced_tick_exp)
 					continue;
 				rdp->rcu_forced_tick_exp = true;
-				tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP);
+				preempt_disable();
+				if (cpu_online(cpu))
+					tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP);
+				preempt_enable();
 			}
 		}
 		j = READ_ONCE(jiffies_till_first_fqs);