Commit f22c1bb6 authored Feb 02, 2013 by Oleg Nesterov

perf: Introduce hw_perf_event->tp_target and ->tp_list



sys_perf_event_open()->perf_init_event(event) is called before
find_get_context(event), this means that event->ctx == NULL when
class->reg(TRACE_REG_PERF_REGISTER/OPEN) is called and thus it
can't know if this event is per-task or system-wide.

This patch adds hw_perf_event->tp_target for PERF_TYPE_TRACEPOINT,
this is analogous to PERF_TYPE_BREAKPOINT/bp_target we already have.
The patch also moves ->bp_target up so that it can overlap with the
new member, this can help the compiler to generate the better code.

trace_uprobe_register() will use it for prefiltering to avoid the
unnecessary breakpoints in mm's we do not want to trace.

->tp_target doesn't have its own reference, but we can rely on the
fact that either sys_perf_event_open() holds a reference, or it is
equal to event->ctx->task. So this pointer is always valid until
free_event().

Also add the "struct list_head tp_list" into this union. It is not
strictly necessary, but it can simplify the next changes and we can
add it for free.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

parent 1b47aefd

include/linux/perf_event.h

+7 −2

Original line number	Diff line number	Diff line
		@@ -135,16 +135,21 @@ struct hw_perf_event {
		struct { /* software */
		struct hrtimer hrtimer;
		};
		struct { /* tracepoint */
		struct task_struct *tp_target;
		/* for tp_event->class */
		struct list_head tp_list;
		};
		#ifdef CONFIG_HAVE_HW_BREAKPOINT
		struct { /* breakpoint */
		struct arch_hw_breakpoint info;
		struct list_head bp_list;
		/*
		* Crufty hack to avoid the chicken and egg
		* problem hw_breakpoint has with context
		* creation and event initalization.
		*/
		struct task_struct *bp_target;
		struct arch_hw_breakpoint info;
		struct list_head bp_list;
		};
		#endif
		};

kernel/events/core.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -6162,11 +6162,14 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,

		if (task) {
		event->attach_state = PERF_ATTACH_TASK;

		if (attr->type == PERF_TYPE_TRACEPOINT)
		event->hw.tp_target = task;
		#ifdef CONFIG_HAVE_HW_BREAKPOINT
		/*
		* hw_breakpoint is a bit difficult here..
		*/
		if (attr->type == PERF_TYPE_BREAKPOINT)
		else if (attr->type == PERF_TYPE_BREAKPOINT)
		event->hw.bp_target = task;
		#endif
		}

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