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uprobes/perf: Avoid uprobe_apply() whenever possible

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uprobe_perf_open/close call the costly uprobe_apply() every time,
we can avoid it if:

	- "nr_systemwide != 0" is not changed.

	- There is another process/thread with the same ->mm.

	- copy_proccess() does inherit_event(). dup_mmap() preserves the
	  inserted breakpoints.

	- event->attr.enable_on_exec == T, we can rely on uprobe_mmap()
	  called by exec/mmap paths.

	- tp_target is exiting. Only _close() checks PF_EXITING, I don't
	  think TRACE_REG_PERF_OPEN can hit the dying task too often.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
This commit is contained in:
Oleg Nesterov 2013-02-04 19:05:43 +01:00
parent f42d24a1d2
commit b2fe8ba674
1 changed files with 36 additions and 6 deletions
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42
kernel/trace/trace_uprobe.c
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@ -680,30 +680,60 @@ __uprobe_perf_filter(struct trace_uprobe_filter *filter, struct mm_struct *mm)
return false;
}
static inline bool
uprobe_filter_event(struct trace_uprobe *tu, struct perf_event *event)
{
return __uprobe_perf_filter(&tu->filter, event->hw.tp_target->mm);
}
static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event)
{
bool done;
write_lock(&tu->filter.rwlock);
if (event->hw.tp_target)
if (event->hw.tp_target) {
/*
* event->parent != NULL means copy_process(), we can avoid
* uprobe_apply(). current->mm must be probed and we can rely
* on dup_mmap() which preserves the already installed bp's.
*
* attr.enable_on_exec means that exec/mmap will install the
* breakpoints we need.
*/
done = tu->filter.nr_systemwide ||
event->parent || event->attr.enable_on_exec ||
uprobe_filter_event(tu, event);
list_add(&event->hw.tp_list, &tu->filter.perf_events);
else
} else {
done = tu->filter.nr_systemwide;
tu->filter.nr_systemwide++;
}
write_unlock(&tu->filter.rwlock);
uprobe_apply(tu->inode, tu->offset, &tu->consumer, true);
if (!done)
uprobe_apply(tu->inode, tu->offset, &tu->consumer, true);
return 0;
}
static int uprobe_perf_close(struct trace_uprobe *tu, struct perf_event *event)
{
bool done;
write_lock(&tu->filter.rwlock);
if (event->hw.tp_target)
if (event->hw.tp_target) {
list_del(&event->hw.tp_list);
else
done = tu->filter.nr_systemwide ||
(event->hw.tp_target->flags & PF_EXITING) ||
uprobe_filter_event(tu, event);
} else {
tu->filter.nr_systemwide--;
done = tu->filter.nr_systemwide;
}
write_unlock(&tu->filter.rwlock);
uprobe_apply(tu->inode, tu->offset, &tu->consumer, false);
if (!done)
uprobe_apply(tu->inode, tu->offset, &tu->consumer, false);
return 0;
}