kernel/exit: Compute 'current' directly

This patch effectively replaces the tsk pointer dereference (which is
obviously == current), to directly use get_current() macro. In this
case, do_exit() always passes current to exit_mm(), hence we can
simply get rid of the argument. This is also a performance win on some
archs such as x86-64 and ppc64 -- arm64 is no longer an issue.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Cc: mark.rutland@arm.com
Link: http://lkml.kernel.org/r/1483479794-14013-2-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index 8f14b866f9f616adcf13f2fde5c5652fb113cb42..2385d434a46eeffd1d36450a1dad590c8eeaff41 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -468,12 +468,12 @@ assign_new_owner:
  * Turn us into a lazy TLB process if we
  * aren't already..
  */
-static void exit_mm(struct task_struct *tsk)
+static void exit_mm(void)
 {
-       struct mm_struct *mm = tsk->mm;
+       struct mm_struct *mm = current->mm;
        struct core_state *core_state;
 
-       mm_release(tsk, mm);
+       mm_release(current, mm);
        if (!mm)
                return;
        sync_mm_rss(mm);
@@ -491,7 +491,7 @@ static void exit_mm(struct task_struct *tsk)
 
                up_read(&mm->mmap_sem);
 
-               self.task = tsk;
+               self.task = current;
                self.next = xchg(&core_state->dumper.next, &self);
                /*
                 * Implies mb(), the result of xchg() must be visible
@@ -501,22 +501,22 @@ static void exit_mm(struct task_struct *tsk)
                        complete(&core_state->startup);
 
                for (;;) {
-                       set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+                       set_task_state(current, TASK_UNINTERRUPTIBLE);
                        if (!self.task) /* see coredump_finish() */
                                break;
                        freezable_schedule();
                }
-               __set_task_state(tsk, TASK_RUNNING);
+               __set_task_state(current, TASK_RUNNING);
                down_read(&mm->mmap_sem);
        }
        atomic_inc(&mm->mm_count);
-       BUG_ON(mm != tsk->active_mm);
+       BUG_ON(mm != current->active_mm);
        /* more a memory barrier than a real lock */
-       task_lock(tsk);
-       tsk->mm = NULL;
+       task_lock(current);
+       current->mm = NULL;
        up_read(&mm->mmap_sem);
        enter_lazy_tlb(mm, current);
-       task_unlock(tsk);
+       task_unlock(current);
        mm_update_next_owner(mm);
        mmput(mm);
        if (test_thread_flag(TIF_MEMDIE))
@@ -823,7 +823,7 @@ void __noreturn do_exit(long code)
        tsk->exit_code = code;
        taskstats_exit(tsk, group_dead);
 
-       exit_mm(tsk);
+       exit_mm();
 
        if (group_dead)
                acct_process();