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perf,hw_breakpoint: Initialize hardware api earlier

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When using early debugging, the kernel does not initialize the
hw_breakpoint API early enough and causes the late initialization of
the kernel debugger to fail. The boot arguments are:

    earlyprintk=vga ekgdboc=kbd kgdbwait

Then simply type "go" at the kdb prompt and boot. The kernel will
later emit the message:

    kgdb: Could not allocate hwbreakpoints

And at that point the kernel debugger will cease to work correctly.

The solution is to initialize the hw_breakpoint at the same time that
all the other perf call backs are initialized instead of using a
core_initcall() initialization which happens well after the kernel
debugger can make use of hardware breakpoints.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4CD3396D.1090308@windriver.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Jason Wessel 2010-11-04 17:33:01 -05:00 committed by Frederic Weisbecker
parent 6c0aca288e
commit 3c502e7a02
3 changed files with 11 additions and 2 deletions
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4
include/linux/hw_breakpoint.h
View file

@ -33,6 +33,8 @@ enum bp_type_idx {
#ifdef CONFIG_HAVE_HW_BREAKPOINT
extern int __init init_hw_breakpoint(void);
static inline void hw_breakpoint_init(struct perf_event_attr *attr)
{
memset(attr, 0, sizeof(*attr));
@ -108,6 +110,8 @@ static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
#else /* !CONFIG_HAVE_HW_BREAKPOINT */
static inline int __init init_hw_breakpoint(void) { return 0; }
static inline struct perf_event *
register_user_hw_breakpoint(struct perf_event_attr *attr,
perf_overflow_handler_t triggered,

3
kernel/hw_breakpoint.c
View file

@ -620,7 +620,7 @@ static struct pmu perf_breakpoint = {
.read = hw_breakpoint_pmu_read,
};
static int __init init_hw_breakpoint(void)
int __init init_hw_breakpoint(void)
{
unsigned int **task_bp_pinned;
int cpu, err_cpu;
@ -655,6 +655,5 @@ static int __init init_hw_breakpoint(void)
return -ENOMEM;
}
core_initcall(init_hw_breakpoint);

6
kernel/perf_event.c
View file

@ -31,6 +31,7 @@
#include <linux/kernel_stat.h>
#include <linux/perf_event.h>
#include <linux/ftrace_event.h>
#include <linux/hw_breakpoint.h>
#include <asm/irq_regs.h>
@ -6295,6 +6296,8 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
void __init perf_event_init(void)
{
int ret;
perf_event_init_all_cpus();
init_srcu_struct(&pmus_srcu);
perf_pmu_register(&perf_swevent);
@ -6302,4 +6305,7 @@ void __init perf_event_init(void)
perf_pmu_register(&perf_task_clock);
perf_tp_register();
perf_cpu_notifier(perf_cpu_notify);
ret = init_hw_breakpoint();
WARN(ret, "hw_breakpoint initialization failed with: %d", ret);
}