Commit 3c502e7a authored by Jason Wessel's avatar Jason Wessel Committed by Frederic Weisbecker
Browse files

perf,hw_breakpoint: Initialize hardware api earlier 



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: default avatarJason 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: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 6c0aca28

include/linux/hw_breakpoint.h

+4 −0
Original line number Diff line number Diff line
@@ -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,

kernel/hw_breakpoint.c

+1 −2
Original line number Diff line number Diff line
@@ -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);

kernel/perf_event.c

+6 −0
Original line number Diff line number Diff line
@@ -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);

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE