Messages in this thread Patch in this message | | | Date | Thu, 04 Nov 2010 17:53:33 -0500 | From | Jason Wessel <> | Subject | [PATCH] perf,hw_breakpoint: Initialize hardware api earlier |
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Hi Frederic,
Per our conversation, here is a possible patch to fix the early debugging. It might be the case that you can kill off the return code from the init_hw_breakpoint(), or at least do something with it. It was not obvious to me what you might want to emit for a mess or act on if the initialization fails.
Thanks, Jason.
-- From 7c425dba3a4522343faf3519f3d0e99e2e55f30c Mon Sep 17 00:00:00 2001 From: Jason Wessel <jason.wessel@windriver.com> Date: Thu, 4 Nov 2010 17:33:01 -0500 Subject: [PATCH] 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: 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> --- include/linux/hw_breakpoint.h | 4 ++++ kernel/hw_breakpoint.c | 3 +-- kernel/perf_event.c | 2 ++ 3 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index a2d6ea4..d9d1799 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -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 extern 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, diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c index 2c9120f..e532582 100644 --- a/kernel/hw_breakpoint.c +++ b/kernel/hw_breakpoint.c @@ -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); diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 517d827..b1eb5c6 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -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> @@ -6302,4 +6303,5 @@ void __init perf_event_init(void) perf_pmu_register(&perf_task_clock); perf_tp_register(); perf_cpu_notifier(perf_cpu_notify); + init_hw_breakpoint(); } -- 1.6.3.3
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