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tracing/rb: Convert to hotplug state machine 

Install the callbacks via the state machine. The notifier in struct
ring_buffer is replaced by the multi instance interface.  Upon
__ring_buffer_alloc() invocation, cpuhp_state_add_instance() will invoke
the trace_rb_cpu_prepare() on each CPU.

This callback may now fail. This means __ring_buffer_alloc() will fail and
cleanup (like previously) and during a CPU up event this failure will not
allow the CPU to come up.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161126231350.10321-7-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Sebastian Andrzej Siewior 2016-11-27 00:13:34 +01:00 committed by Thomas Gleixner
parent 14660b7ea3
commit b32614c034
4 changed files with 65 additions and 90 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/cpuhotplug.h
View File

@ -62,6 +62,7 @@ enum cpuhp_state {
CPUHP_TOPOLOGY_PREPARE,
CPUHP_NET_IUCV_PREPARE,
CPUHP_ARM_BL_PREPARE,
CPUHP_TRACE_RB_PREPARE,
CPUHP_TIMERS_DEAD,
CPUHP_NOTF_ERR_INJ_PREPARE,
CPUHP_MIPS_SOC_PREPARE,

6
include/linux/ring_buffer.h
View File

@ -198,4 +198,10 @@ enum ring_buffer_flags {
RB_FL_OVERWRITE = 1 << 0,
};
#ifdef CONFIG_RING_BUFFER
int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node);
#else
#define trace_rb_cpu_prepare NULL
#endif
#endif /* _LINUX_RING_BUFFER_H */

133
kernel/trace/ring_buffer.c
View File

@ -479,9 +479,7 @@ struct ring_buffer {
struct ring_buffer_per_cpu **buffers;
#ifdef CONFIG_HOTPLUG_CPU
struct notifier_block cpu_notify;
#endif
struct hlist_node node;
u64 (*clock)(void);
struct rb_irq_work irq_work;
@ -1274,11 +1272,6 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
kfree(cpu_buffer);
}
#ifdef CONFIG_HOTPLUG_CPU
static int rb_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu);
#endif
/**
* __ring_buffer_alloc - allocate a new ring_buffer
* @size: the size in bytes per cpu that is needed.
@ -1296,6 +1289,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
long nr_pages;
int bsize;
int cpu;
int ret;
/* keep it in its own cache line */
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
@ -1318,17 +1312,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
if (nr_pages < 2)
nr_pages = 2;
/*
* 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
cpu_notifier_register_begin();
cpumask_copy(buffer->cpumask, cpu_online_mask);
#else
cpumask_copy(buffer->cpumask, cpu_possible_mask);
#endif
buffer->cpus = nr_cpu_ids;
bsize = sizeof(void *) * nr_cpu_ids;
@ -1337,19 +1320,15 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
if (!buffer->buffers)
goto fail_free_cpumask;
for_each_buffer_cpu(buffer, cpu) {
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu])
goto fail_free_buffers;
}
cpu = raw_smp_processor_id();
cpumask_set_cpu(cpu, buffer->cpumask);
buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu])
goto fail_free_buffers;
#ifdef CONFIG_HOTPLUG_CPU
buffer->cpu_notify.notifier_call = rb_cpu_notify;
buffer->cpu_notify.priority = 0;
__register_cpu_notifier(&buffer->cpu_notify);
cpu_notifier_register_done();
#endif
ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
if (ret < 0)
goto fail_free_buffers;
mutex_init(&buffer->mutex);
@ -1364,9 +1343,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
fail_free_cpumask:
free_cpumask_var(buffer->cpumask);
#ifdef CONFIG_HOTPLUG_CPU
cpu_notifier_register_done();
#endif
fail_free_buffer:
kfree(buffer);
@ -1383,18 +1359,11 @@ ring_buffer_free(struct ring_buffer *buffer)
{
int cpu;
#ifdef CONFIG_HOTPLUG_CPU
cpu_notifier_register_begin();
__unregister_cpu_notifier(&buffer->cpu_notify);
#endif
cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
for_each_buffer_cpu(buffer, cpu)
rb_free_cpu_buffer(buffer->buffers[cpu]);
#ifdef CONFIG_HOTPLUG_CPU
cpu_notifier_register_done();
#endif
kfree(buffer->buffers);
free_cpumask_var(buffer->cpumask);
@ -4633,62 +4602,48 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
}
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
#ifdef CONFIG_HOTPLUG_CPU
static int rb_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
/*
* We only allocate new buffers, never free them if the CPU goes down.
* If we were to free the buffer, then the user would lose any trace that was in
* the buffer.
*/
int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
{
struct ring_buffer *buffer =
container_of(self, struct ring_buffer, cpu_notify);
long cpu = (long)hcpu;
struct ring_buffer *buffer;
long nr_pages_same;
int cpu_i;
unsigned long nr_pages;
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
if (cpumask_test_cpu(cpu, buffer->cpumask))
return NOTIFY_OK;
buffer = container_of(node, struct ring_buffer, node);
if (cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
nr_pages = 0;
nr_pages_same = 1;
/* check if all cpu sizes are same */
for_each_buffer_cpu(buffer, cpu_i) {
/* fill in the size from first enabled cpu */
if (nr_pages == 0)
nr_pages = buffer->buffers[cpu_i]->nr_pages;
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
nr_pages_same = 0;
break;
}
nr_pages = 0;
nr_pages_same = 1;
/* check if all cpu sizes are same */
for_each_buffer_cpu(buffer, cpu_i) {
/* fill in the size from first enabled cpu */
if (nr_pages == 0)
nr_pages = buffer->buffers[cpu_i]->nr_pages;
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
nr_pages_same = 0;
break;
}
/* allocate minimum pages, user can later expand it */
if (!nr_pages_same)
nr_pages = 2;
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu]) {
WARN(1, "failed to allocate ring buffer on CPU %ld\n",
cpu);
return NOTIFY_OK;
}
smp_wmb();
cpumask_set_cpu(cpu, buffer->cpumask);
break;
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
/*
* Do nothing.
* If we were to free the buffer, then the user would
* lose any trace that was in the buffer.
*/
break;
default:
break;
}
return NOTIFY_OK;
/* allocate minimum pages, user can later expand it */
if (!nr_pages_same)
nr_pages = 2;
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu]) {
WARN(1, "failed to allocate ring buffer on CPU %u\n",
cpu);
return -ENOMEM;
}
smp_wmb();
cpumask_set_cpu(cpu, buffer->cpumask);
return 0;
}
#endif
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
/*

15
kernel/trace/trace.c
View File

@ -7659,10 +7659,21 @@ __init static int tracer_alloc_buffers(void)
raw_spin_lock_init(&global_trace.start_lock);
/*
* The prepare callbacks allocates some memory for the ring buffer. We
* don't free the buffer if the if the CPU goes down. If we were to free
* the buffer, then the user would lose any trace that was in the
* buffer. The memory will be removed once the "instance" is removed.
*/
ret = cpuhp_setup_state_multi(CPUHP_TRACE_RB_PREPARE,
"trace/RB:preapre", trace_rb_cpu_prepare,
NULL);
if (ret < 0)
goto out_free_cpumask;
/* Used for event triggers */
temp_buffer = ring_buffer_alloc(PAGE_SIZE, RB_FL_OVERWRITE);
if (!temp_buffer)
goto out_free_cpumask;
goto out_rm_hp_state;
if (trace_create_savedcmd() < 0)
goto out_free_temp_buffer;
@ -7723,6 +7734,8 @@ out_free_savedcmd:
free_saved_cmdlines_buffer(savedcmd);
out_free_temp_buffer:
ring_buffer_free(temp_buffer);
out_rm_hp_state:
cpuhp_remove_multi_state(CPUHP_TRACE_RB_PREPARE);
out_free_cpumask:
free_cpumask_var(global_trace.tracing_cpumask);
out_free_buffer_mask: