From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Mon, 13 Apr 2020 21:02:07 +0000 (-0400)
Subject: ring buffer backend: remove cpu hotplug compatibility code
X-Git-Tag: for-upstreaming-review-1~19
X-Git-Url: http://git.liburcu.org/?p=lttng-modules.git;a=commitdiff_plain;h=636d6bde2926844c256983fab0344ac06e037acb

ring buffer backend: remove cpu hotplug compatibility code
---

diff --git a/lib/ringbuffer/ring_buffer_backend.c b/lib/ringbuffer/ring_buffer_backend.c
index a9b9acd7..557847c3 100644
--- a/lib/ringbuffer/ring_buffer_backend.c
+++ b/lib/ringbuffer/ring_buffer_backend.c
@@ -252,8 +252,6 @@ void channel_backend_reset(struct channel_backend *chanb)
 	chanb->start_tsc = config->cb.ring_buffer_clock_read(chan);
 }
 
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
-
 /*
  * No need to implement a "dead" callback to do a buffer switch here,
  * because it will happen when tracing is stopped, or will be done by
@@ -284,58 +282,6 @@ int lttng_cpuhp_rb_backend_prepare(unsigned int cpu,
 }
 EXPORT_SYMBOL_GPL(lttng_cpuhp_rb_backend_prepare);
 
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/**
- *	lib_ring_buffer_cpu_hp_callback - CPU hotplug callback
- *	@nb: notifier block
- *	@action: hotplug action to take
- *	@hcpu: CPU number
- *
- *	Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
- */
-static
-int lib_ring_buffer_cpu_hp_callback(struct notifier_block *nb,
-					      unsigned long action,
-					      void *hcpu)
-{
-	unsigned int cpu = (unsigned long)hcpu;
-	struct channel_backend *chanb = container_of(nb, struct channel_backend,
-						     cpu_hp_notifier);
-	const struct lib_ring_buffer_config *config = &chanb->config;
-	struct lib_ring_buffer *buf;
-	int ret;
-
-	CHAN_WARN_ON(chanb, config->alloc == RING_BUFFER_ALLOC_GLOBAL);
-
-	switch (action) {
-	case CPU_UP_PREPARE:
-	case CPU_UP_PREPARE_FROZEN:
-		buf = per_cpu_ptr(chanb->buf, cpu);
-		ret = lib_ring_buffer_create(buf, chanb, cpu);
-		if (ret) {
-			printk(KERN_ERR
-			  "ring_buffer_cpu_hp_callback: cpu %d "
-			  "buffer creation failed\n", cpu);
-			return NOTIFY_BAD;
-		}
-		break;
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		/* No need to do a buffer switch here, because it will happen
-		 * when tracing is stopped, or will be done by switch timer CPU
-		 * DEAD callback. */
-		break;
-	}
-	return NOTIFY_OK;
-}
-
-#endif
-
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-
 /**
  * channel_backend_init - initialize a channel backend
  * @chanb: channel backend
@@ -412,50 +358,11 @@ int channel_backend_init(struct channel_backend *chanb,
 		if (!chanb->buf)
 			goto free_cpumask;
 
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
 		chanb->cpuhp_prepare.component = LTTNG_RING_BUFFER_BACKEND;
 		ret = cpuhp_state_add_instance(lttng_rb_hp_prepare,
 			&chanb->cpuhp_prepare.node);
 		if (ret)
 			goto free_bufs;
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-
-		{
-			/*
-			 * In case of non-hotplug cpu, if the ring-buffer is allocated
-			 * in early initcall, it will not be notified of secondary cpus.
-			 * In that off case, we need to allocate for all possible cpus.
-			 */
-#ifdef CONFIG_HOTPLUG_CPU
-			/*
-			 * buf->backend.allocated test takes care of concurrent CPU
-			 * hotplug.
-			 * Priority higher than frontend, so we create the ring buffer
-			 * before we start the timer.
-			 */
-			chanb->cpu_hp_notifier.notifier_call =
-					lib_ring_buffer_cpu_hp_callback;
-			chanb->cpu_hp_notifier.priority = 5;
-			register_hotcpu_notifier(&chanb->cpu_hp_notifier);
-
-			get_online_cpus();
-			for_each_online_cpu(i) {
-				ret = lib_ring_buffer_create(per_cpu_ptr(chanb->buf, i),
-							 chanb, i);
-				if (ret)
-					goto free_bufs;	/* cpu hotplug locked */
-			}
-			put_online_cpus();
-#else
-			for_each_possible_cpu(i) {
-				ret = lib_ring_buffer_create(per_cpu_ptr(chanb->buf, i),
-							 chanb, i);
-				if (ret)
-					goto free_bufs;
-			}
-#endif
-		}
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
 	} else {
 		chanb->buf = kzalloc(sizeof(struct lib_ring_buffer), GFP_KERNEL);
 		if (!chanb->buf)
@@ -470,18 +377,11 @@ int channel_backend_init(struct channel_backend *chanb,
 
 free_bufs:
 	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
 		/*
 		 * Teardown of lttng_rb_hp_prepare instance
 		 * on "add" error is handled within cpu hotplug,
 		 * no teardown to do from the caller.
 		 */
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-#ifdef CONFIG_HOTPLUG_CPU
-		put_online_cpus();
-		unregister_hotcpu_notifier(&chanb->cpu_hp_notifier);
-#endif
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
 		for_each_possible_cpu(i) {
 			struct lib_ring_buffer *buf =
 				per_cpu_ptr(chanb->buf, i);
@@ -510,15 +410,11 @@ void channel_backend_unregister_notifiers(struct channel_backend *chanb)
 	const struct lib_ring_buffer_config *config = &chanb->config;
 
 	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
 		int ret;
 
 		ret = cpuhp_state_remove_instance(lttng_rb_hp_prepare,
 				&chanb->cpuhp_prepare.node);
 		WARN_ON(ret);
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-		unregister_hotcpu_notifier(&chanb->cpu_hp_notifier);
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
 	}
 }