Le Fri, Apr 11, 2025 at 12:41:37PM -0500, Junxuan Liao a écrit :
>
> > > Are you interested in working on joining the noble quest of getting the
> > > rest of the nohz_full support in place? (Full disclosure: This stuff
> > > is non-trivial.)
> >
> > I believe the request is more of just tracing entry and exit from the
> > kernel, which just needs a simple trace event at the border crossings.
>
> Yeah I'm more interested in just tracing this for now.
>
> > It's been on my todo list to add one for page
> > fault exit (as I do care for how long they last.
>
> I've added a tracepoint similar to page_fault_user for that but I'm not
> sure if it's the best way to do it. Should I send a patch for review?
If you do so, it may be a good idea to remove page_fault_user and
page_fault_kernel and introduce page_fault_user_enter/page_fault_user_exit
and page_fault_kernel_enter/page_fault_kernel_exit.
But the following is also possible (and then trace/events/context_tracking.h
should be renamed into trace/events/entry.h):
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index fc61d0205c97..83b1764078f7 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -15,6 +15,8 @@
#include <asm/entry-common.h>
+#include <trace/events/context_tracking.h>
+
/*
* Define dummy _TIF work flags if not defined by the architecture or for
* disabled functionality.
@@ -115,6 +117,7 @@ static __always_inline void enter_from_user_mode(struct
pt_regs *regs)
instrumentation_begin();
kmsan_unpoison_entry_regs(regs);
trace_hardirqs_off_finish();
+ trace_user_exit(0);
instrumentation_end();
}
@@ -357,6 +360,7 @@ static __always_inline void
exit_to_user_mode_prepare(struct pt_regs *regs)
static __always_inline void exit_to_user_mode(void)
{
instrumentation_begin();
+ trace_user_enter(0);
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare();
instrumentation_end();
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index fb5be6e9b423..e9395936bded 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -428,9 +428,6 @@ static __always_inline void ct_kernel_enter(bool user, int
offset) { }
#ifdef CONFIG_CONTEXT_TRACKING_USER
-#define CREATE_TRACE_POINTS
-#include <trace/events/context_tracking.h>
-
DEFINE_STATIC_KEY_FALSE_RO(context_tracking_key);
EXPORT_SYMBOL_GPL(context_tracking_key);
@@ -486,7 +483,6 @@ void noinstr __ct_user_enter(enum ctx_state state)
*/
if (state == CT_STATE_USER) {
instrumentation_begin();
- trace_user_enter(0);
vtime_user_enter(current);
instrumentation_end();
}
@@ -623,7 +619,6 @@ void noinstr __ct_user_exit(enum ctx_state state)
if (state == CT_STATE_USER) {
instrumentation_begin();
vtime_user_exit(current);
- trace_user_exit(0);
instrumentation_end();
}
--
Frederic Weisbecker
SUSE Labs
