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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>
This commit is contained in:
Richard Weinberger 2016-08-18 14:57:17 +02:00 committed by Thomas Gleixner
parent 017c59c042
commit e6d4989a9a
4 changed files with 26 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/cpuhotplug.h
View File

@ -21,6 +21,7 @@ enum cpuhp_state {
CPUHP_PROFILE_PREPARE,
CPUHP_X2APIC_PREPARE,
CPUHP_SMPCFD_PREPARE,
CPUHP_RELAY_PREPARE,
CPUHP_RCUTREE_PREP,
CPUHP_NOTIFY_PREPARE,
CPUHP_TIMERS_DEAD,

6
include/linux/relay.h
View File

@ -288,5 +288,11 @@ static inline void subbuf_start_reserve(struct rchan_buf *buf,
*/
extern const struct file_operations relay_file_operations;
#ifdef CONFIG_RELAY
int relay_prepare_cpu(unsigned int cpu);
#else
#define relay_prepare_cpu NULL
#endif
#endif /* _LINUX_RELAY_H */

6
kernel/cpu.c
View File

@ -23,6 +23,7 @@
#include <linux/tick.h>
#include <linux/irq.h>
#include <linux/smpboot.h>
#include <linux/relay.h>
#include <trace/events/power.h>
#define CREATE_TRACE_POINTS
@ -1272,6 +1273,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
.startup.single = smpcfd_prepare_cpu,
.teardown.single = smpcfd_dead_cpu,
},
[CPUHP_RELAY_PREPARE] = {
.name = "relay:prepare",
.startup.single = relay_prepare_cpu,
.teardown.single = NULL,
},
[CPUHP_RCUTREE_PREP] = {
.name = "RCU/tree:prepare",
.startup.single = rcutree_prepare_cpu,

58
kernel/relay.c
View File

@ -513,48 +513,25 @@ static void setup_callbacks(struct rchan *chan,
chan->cb = cb;
}
/**
* relay_hotcpu_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 relay_hotcpu_callback(struct notifier_block *nb,
unsigned long action,
void *hcpu)
int relay_prepare_cpu(unsigned int cpu)
{
unsigned int hotcpu = (unsigned long)hcpu;
struct rchan *chan;
struct rchan_buf *buf;
switch(action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
mutex_lock(&relay_channels_mutex);
list_for_each_entry(chan, &relay_channels, list) {
if ((buf = *per_cpu_ptr(chan->buf, hotcpu)))
continue;
buf = relay_open_buf(chan, hotcpu);
if (!buf) {
printk(KERN_ERR
"relay_hotcpu_callback: cpu %d buffer "
"creation failed\n", hotcpu);
mutex_unlock(&relay_channels_mutex);
return notifier_from_errno(-ENOMEM);
}
*per_cpu_ptr(chan->buf, hotcpu) = buf;
mutex_lock(&relay_channels_mutex);
list_for_each_entry(chan, &relay_channels, list) {
if ((buf = *per_cpu_ptr(chan->buf, cpu)))
continue;
buf = relay_open_buf(chan, cpu);
if (!buf) {
pr_err("relay: cpu %d buffer creation failed\n", cpu);
mutex_unlock(&relay_channels_mutex);
return -ENOMEM;
}
mutex_unlock(&relay_channels_mutex);
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
/* No need to flush the cpu : will be flushed upon
* final relay_flush() call. */
break;
*per_cpu_ptr(chan->buf, cpu) = buf;
}
return NOTIFY_OK;
mutex_unlock(&relay_channels_mutex);
return 0;
}
/**
@ -1387,12 +1364,3 @@ const struct file_operations relay_file_operations = {
.splice_read = relay_file_splice_read,
};
EXPORT_SYMBOL_GPL(relay_file_operations);
static __init int relay_init(void)
{
hotcpu_notifier(relay_hotcpu_callback, 0);
return 0;
}
early_initcall(relay_init);