sched: add do_sched_yield() helper; remove in-kernel call to sched_yield()

Using the sched-internal do_sched_yield() helper allows us to get rid of
the sched-internal call to the sys_sched_yield() syscall.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527[email protected]

Cc: Ingo Molnar <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Dominik Brodowski <[email protected]>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e7c535eee0a6d493a2a43eba210c08c6858b63d1..8de4919c889a9ee2b80fee555312d121dc813daa 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4892,7 +4892,7 @@ SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
  *
  * Return: 0.
  */
-SYSCALL_DEFINE0(sched_yield)
+static void do_sched_yield(void)
 {
        struct rq_flags rf;
        struct rq *rq;
@@ -4913,7 +4913,11 @@ SYSCALL_DEFINE0(sched_yield)
        sched_preempt_enable_no_resched();
 
        schedule();
+}
 
+SYSCALL_DEFINE0(sched_yield)
+{
+       do_sched_yield();
        return 0;
 }
 
@@ -4997,7 +5001,7 @@ EXPORT_SYMBOL(__cond_resched_softirq);
 void __sched yield(void)
 {
        set_current_state(TASK_RUNNING);
-       sys_sched_yield();
+       do_sched_yield();
 }
 EXPORT_SYMBOL(yield);