tree 1bd1defbfe3f285dfa7c77f94bc5523ac4a82679
parent f42d24a1d20d2e72d1e5d48930f18b138dfad117
author Oleg Nesterov <oleg@redhat.com> 1360001143 +0100
committer Oleg Nesterov <oleg@redhat.com> 1360344488 +0100

uprobes/perf: Avoid uprobe_apply() whenever possible

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>