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hw_breakpoint: Add modify_bp_slot() function

Browse source 
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: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Hari Bathini <[email protected]>
Cc: Jin Yao <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Milind Chabbi <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sukadev Bhattiprolu <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Jiri Olsa 2018-03-12 14:45:43 +01:00 • committed by Ingo Molnar
commit ea6a9d530c
1 changed files with 39 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

46
kernel/events/hw_breakpoint.c
View file

@ -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);