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Commit ea6a9d53 authored by Jiri Olsa's avatar Jiri Olsa Committed by Ingo Molnar
Browse files

hw_breakpoint: Add modify_bp_slot() function 



Add the modify_bp_slot() function to keep slot numbers
correct when changing the breakpoint type.

Using existing __release_bp_slot()/__reserve_bp_slot()
call sequence to update the slot counts.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20180312134548.31532-4-jolsa@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1ad9ff7d

kernel/events/hw_breakpoint.c

+39 −7
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ 
#include <linux/list.h>

#include <linux/cpu.h>

#include <linux/smp.h>

#include <linux/bug.h>



#include <linux/hw_breakpoint.h>

/*
@@ -344,6 +345,38 @@ void release_bp_slot(struct perf_event *bp) 
	mutex_unlock(&nr_bp_mutex);

}



static int __modify_bp_slot(struct perf_event *bp, u64 old_type)

{

	int err;



	__release_bp_slot(bp, old_type);



	err = __reserve_bp_slot(bp, bp->attr.bp_type);

	if (err) {

		/*

		 * Reserve the old_type slot back in case

		 * there's no space for the new type.

		 *

		 * This must succeed, because we just released

		 * the old_type slot in the __release_bp_slot

		 * call above. If not, something is broken.

		 */

		WARN_ON(__reserve_bp_slot(bp, old_type));

	}



	return err;

}



static int modify_bp_slot(struct perf_event *bp, u64 old_type)

{

	int ret;



	mutex_lock(&nr_bp_mutex);

	ret = __modify_bp_slot(bp, old_type);

	mutex_unlock(&nr_bp_mutex);

	return ret;

}



/*

 * Allow the kernel debugger to reserve breakpoint slots without

 * taking a lock using the dbg_* variant of for the reserve and
@@ -435,6 +468,7 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att 
	u64 old_addr = bp->attr.bp_addr;

	u64 old_len = bp->attr.bp_len;

	int old_type = bp->attr.bp_type;

	bool modify = attr->bp_type != old_type;

	int err = 0;



	/*
@@ -452,12 +486,9 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att 
	bp->attr.bp_type = attr->bp_type;

	bp->attr.bp_len = attr->bp_len;



	if (attr->disabled)

		goto end;



	err = validate_hw_breakpoint(bp);

	if (!err)

		perf_event_enable(bp);

	if (!err && modify)

		err = modify_bp_slot(bp, old_type);



	if (err) {

		bp->attr.bp_addr = old_addr;
@@ -469,9 +500,10 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att 
		return err;

	}



end:

	bp->attr.disabled = attr->disabled;

	if (!attr->disabled)

		perf_event_enable(bp);



	bp->attr.disabled = attr->disabled;

	return 0;

}

EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);