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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>
hifive-unleashed-5.1
Oleg Nesterov 2013-02-02 16:27:52 +01:00
parent 1b47aefd9b
commit f22c1bb6b4
2 changed files with 11 additions and 3 deletions
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9
include/linux/perf_event.h
View File

@ -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
};

5
kernel/events/core.c
View File

@ -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
}