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Merge branch 'tip/tracing/core/devel' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into tracing/ftrace

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Conflicts:
	kernel/trace/trace_hw_branches.c
This commit is contained in:
Ingo Molnar 2009-02-09 10:35:12 +01:00
commit 44b0635481
13 changed files with 85 additions and 44 deletions
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31
kernel/trace/ring_buffer.c
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@ -4,9 +4,11 @@
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*/
#include <linux/ring_buffer.h>
#include <linux/ftrace_irq.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/mutex.h>
@ -982,6 +984,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer *buffer = cpu_buffer->buffer;
struct ring_buffer_event *event;
unsigned long flags;
bool lock_taken = false;
commit_page = cpu_buffer->commit_page;
/* we just need to protect against interrupts */
@ -995,7 +998,30 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *next_page = tail_page;
local_irq_save(flags);
__raw_spin_lock(&cpu_buffer->lock);
/*
* Since the write to the buffer is still not
* fully lockless, we must be careful with NMIs.
* The locks in the writers are taken when a write
* crosses to a new page. The locks protect against
* races with the readers (this will soon be fixed
* with a lockless solution).
*
* Because we can not protect against NMIs, and we
* want to keep traces reentrant, we need to manage
* what happens when we are in an NMI.
*
* NMIs can happen after we take the lock.
* If we are in an NMI, only take the lock
* if it is not already taken. Otherwise
* simply fail.
*/
if (unlikely(in_nmi())) {
if (!__raw_spin_trylock(&cpu_buffer->lock))
goto out_unlock;
} else
__raw_spin_lock(&cpu_buffer->lock);
lock_taken = true;
rb_inc_page(cpu_buffer, &next_page);
@ -1097,7 +1123,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
if (tail <= BUF_PAGE_SIZE)
local_set(&tail_page->write, tail);
__raw_spin_unlock(&cpu_buffer->lock);
if (likely(lock_taken))
__raw_spin_unlock(&cpu_buffer->lock);
local_irq_restore(flags);
return NULL;
}