[patch part-II V2 13/13] x86/entry/common: Split irq tracing in prepare_exit_to_usermode()

Thomas Gleixner
2020-03-08T23:25:32Z

As in entry from user mode, lockdep and tracing have different
requirements. lockdep needs to know about the interrupts off state accross
the call to user_enter_irqsoff() but tracing is unsafe after the call.

Split it up and tell the tracer that interrupts are going to be enabled
before calling user_enter_irqsoff() and tell lockdep afterwards.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/entry/common.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -251,9 +251,19 @@ static noinline void __prepare_exit_to_u
{
__prepare_exit_to_usermode(regs);

+ /*
+ * Return to user space enables interrupts. Tell the tracer before
+ * invoking user_enter_irqsoff() which switches to CONTEXT_USER and
+ * RCU to rcuidle state. Lockdep still needs to keep the irqs
+ * disabled state.
+ */
+ __trace_hardirqs_on();
+
user_enter_irqoff();
mds_user_clear_cpu_buffers();
- trace_hardirqs_on();
+
+ /* All done. Tell lockdep as well. */
+ lockdep_hardirqs_on(CALLER_ADDR0);
}
NOKPROBE_SYMBOL(prepare_exit_to_usermode);