linux-kernel - [PATCH v3 04/11] smp: replace smp_call_function_single() with smp

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Date:   Tue, 17 May 2022 14:03:19 -0400
From:   Donghai Qiao <dqiao@...hat.com>
To:     akpm@...ux-foundation.org, sfr@...b.auug.org.au, arnd@...db.de,
        peterz@...radead.org, heying24@...wei.com,
        andriy.shevchenko@...ux.intel.com, axboe@...nel.dk,
        rdunlap@...radead.org, tglx@...utronix.de, gor@...ux.ibm.com
Cc:     donghai.w.qiao@...il.com, linux-kernel@...r.kernel.org,
        Donghai Qiao <dqiao@...hat.com>
Subject: [PATCH v3 04/11] smp: replace smp_call_function_single() with  smp_call()

Eliminated the percpu global csd_data and temporarily hooked up
smp_call_function_single() to smp_call().

Signed-off-by: Donghai Qiao <dqiao@...hat.com>
---
v1 -> v2: Removed 'x' from the function names and change XCALL to
	  SMP_CALL from the new macros
 kernel/smp.c | 74 ++++++++++++++++++----------------------------------
 1 file changed, 25 insertions(+), 49 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 101a48d1d8af..8fdea9547502 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -414,8 +414,6 @@ static __always_inline void csd_unlock(struct __call_single_data *csd)
 	smp_store_release(&csd->node.u_flags, 0);
 }
 
-static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data);
-
 void __smp_call_single_queue(int cpu, struct llist_node *node)
 {
 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
@@ -649,6 +647,9 @@ void flush_smp_call_function_from_idle(void)
 }
 
 /*
+ * This is a temporarily hook up. This function will be eliminated
+ * with a later patch in this series.
+ *
  * smp_call_function_single - Run a function on a specific CPU
  * @func: The function to run. This must be fast and non-blocking.
  * @info: An arbitrary pointer to pass to the function.
@@ -657,59 +658,21 @@ void flush_smp_call_function_from_idle(void)
  * Returns 0 on success, else a negative status code.
  */
 int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
-			     int wait)
+			int wait)
 {
-	call_single_data_t *csd;
-	call_single_data_t csd_stack = {
-		.node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, },
-	};
-	int this_cpu;
-	int err;
-
-	/*
-	 * prevent preemption and reschedule on another processor,
-	 * as well as CPU removal
-	 */
-	this_cpu = get_cpu();
-
-	/*
-	 * Can deadlock when called with interrupts disabled.
-	 * We allow cpu's that are not yet online though, as no one else can
-	 * send smp call function interrupt to this cpu and as such deadlocks
-	 * can't happen.
-	 */
-	WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
-		     && !oops_in_progress);
+	unsigned int flags = 0;
 
-	/*
-	 * When @wait we can deadlock when we interrupt between llist_add() and
-	 * arch_send_call_function_ipi*(); when !@...t we can deadlock due to
-	 * csd_lock() on because the interrupt context uses the same csd
-	 * storage.
-	 */
-	WARN_ON_ONCE(!in_task());
-
-	csd = &csd_stack;
-	if (!wait) {
-		csd = this_cpu_ptr(&csd_data);
-		csd_lock(csd);
-	}
-
-	csd->func = func;
-	csd->info = info;
-#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
-	csd->node.src = smp_processor_id();
-	csd->node.dst = cpu;
-#endif
-
-	err = generic_exec_single(cpu, csd);
+	if ((unsigned int)cpu >= nr_cpu_ids || !cpu_online(cpu))
+		return -ENXIO;
 
 	if (wait)
-		csd_lock_wait(csd);
+		flags = SMP_CALL_TYPE_SYNC;
+	else
+		flags = SMP_CALL_TYPE_ASYNC;
 
-	put_cpu();
+	smp_call(cpu, func, info, flags);
 
-	return err;
+	return 0;
 }
 EXPORT_SYMBOL(smp_call_function_single);
 
@@ -1175,6 +1138,19 @@ void __smp_call_mask_cond(const struct cpumask *mask,
 		smp_cond_func_t cond_func, bool local_cpu,
 		unsigned int flags)
 {
+	bool wait = false;
+
+	if (flags == SMP_CALL_TYPE_SYNC)
+		wait = true;
+
+	preempt_disable();
+
+	/*
+	 * This is temporarily hook. The function smp_call_function_many_cond()
+	 * will be inlined here with a later patch in this series.
+	 */
+	smp_call_function_many_cond(mask, func, info, local_cpu, wait, cond_func);
+	preempt_enable();
 }
 
 /*
-- 
2.27.0