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relayfs: Convert to hotplug state machine
Install the callbacks via the state machine. They are installed at run time but relay_prepare_cpu() does not need to be invoked by the boot CPU because relay_open() was not yet invoked and there are no pools that need to be created. Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: rt@linutronix.de Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20160818125731.27256-3-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -21,6 +21,7 @@ enum cpuhp_state {
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CPUHP_PROFILE_PREPARE,
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CPUHP_X2APIC_PREPARE,
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CPUHP_SMPCFD_PREPARE,
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CPUHP_RELAY_PREPARE,
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CPUHP_RCUTREE_PREP,
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CPUHP_NOTIFY_PREPARE,
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CPUHP_TIMERS_DEAD,
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@ -288,5 +288,11 @@ static inline void subbuf_start_reserve(struct rchan_buf *buf,
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*/
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extern const struct file_operations relay_file_operations;
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#ifdef CONFIG_RELAY
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int relay_prepare_cpu(unsigned int cpu);
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#else
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#define relay_prepare_cpu NULL
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#endif
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#endif /* _LINUX_RELAY_H */
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@ -23,6 +23,7 @@
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#include <linux/tick.h>
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#include <linux/irq.h>
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#include <linux/smpboot.h>
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#include <linux/relay.h>
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#include <trace/events/power.h>
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#define CREATE_TRACE_POINTS
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@ -1272,6 +1273,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
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.startup.single = smpcfd_prepare_cpu,
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.teardown.single = smpcfd_dead_cpu,
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},
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[CPUHP_RELAY_PREPARE] = {
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.name = "relay:prepare",
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.startup.single = relay_prepare_cpu,
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.teardown.single = NULL,
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},
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[CPUHP_RCUTREE_PREP] = {
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.name = "RCU/tree:prepare",
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.startup.single = rcutree_prepare_cpu,
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@ -513,48 +513,25 @@ static void setup_callbacks(struct rchan *chan,
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chan->cb = cb;
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}
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/**
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* relay_hotcpu_callback - CPU hotplug callback
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* @nb: notifier block
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* @action: hotplug action to take
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* @hcpu: CPU number
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*
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* Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
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*/
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static int relay_hotcpu_callback(struct notifier_block *nb,
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unsigned long action,
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void *hcpu)
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int relay_prepare_cpu(unsigned int cpu)
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{
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unsigned int hotcpu = (unsigned long)hcpu;
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struct rchan *chan;
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struct rchan_buf *buf;
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switch(action) {
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case CPU_UP_PREPARE:
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case CPU_UP_PREPARE_FROZEN:
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mutex_lock(&relay_channels_mutex);
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list_for_each_entry(chan, &relay_channels, list) {
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if ((buf = *per_cpu_ptr(chan->buf, hotcpu)))
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continue;
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buf = relay_open_buf(chan, hotcpu);
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if (!buf) {
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printk(KERN_ERR
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"relay_hotcpu_callback: cpu %d buffer "
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"creation failed\n", hotcpu);
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mutex_unlock(&relay_channels_mutex);
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return notifier_from_errno(-ENOMEM);
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}
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*per_cpu_ptr(chan->buf, hotcpu) = buf;
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mutex_lock(&relay_channels_mutex);
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list_for_each_entry(chan, &relay_channels, list) {
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if ((buf = *per_cpu_ptr(chan->buf, cpu)))
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continue;
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buf = relay_open_buf(chan, cpu);
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if (!buf) {
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pr_err("relay: cpu %d buffer creation failed\n", cpu);
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mutex_unlock(&relay_channels_mutex);
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return -ENOMEM;
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}
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mutex_unlock(&relay_channels_mutex);
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break;
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case CPU_DEAD:
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case CPU_DEAD_FROZEN:
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/* No need to flush the cpu : will be flushed upon
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* final relay_flush() call. */
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break;
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*per_cpu_ptr(chan->buf, cpu) = buf;
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}
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return NOTIFY_OK;
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mutex_unlock(&relay_channels_mutex);
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return 0;
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}
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/**
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@ -1387,12 +1364,3 @@ const struct file_operations relay_file_operations = {
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.splice_read = relay_file_splice_read,
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};
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EXPORT_SYMBOL_GPL(relay_file_operations);
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static __init int relay_init(void)
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{
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hotcpu_notifier(relay_hotcpu_callback, 0);
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return 0;
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}
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early_initcall(relay_init);
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