Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86/pti updates from Thomas Gleixner:
 "A mixed bag of fixes and updates for the ghosts which are hunting us.

  The scheduler fixes have been pulled into that branch to avoid
  conflicts.

   - A set of fixes to address a khread_parkme() race which caused lost
     wakeups and loss of state.

   - A deadlock fix for stop_machine() solved by moving the wakeups
     outside of the stopper_lock held region.

   - A set of Spectre V1 array access restrictions. The possible
     problematic spots were discuvered by Dan Carpenters new checks in
     smatch.

   - Removal of an unused file which was forgotten when the rest of that
     functionality was removed"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vdso: Remove unused file
  perf/x86/cstate: Fix possible Spectre-v1 indexing for pkg_msr
  perf/x86/msr: Fix possible Spectre-v1 indexing in the MSR driver
  perf/x86: Fix possible Spectre-v1 indexing for x86_pmu::event_map()
  perf/x86: Fix possible Spectre-v1 indexing for hw_perf_event cache_*
  perf/core: Fix possible Spectre-v1 indexing for ->aux_pages[]
  sched/autogroup: Fix possible Spectre-v1 indexing for sched_prio_to_weight[]
  sched/core: Fix possible Spectre-v1 indexing for sched_prio_to_weight[]
  sched/core: Introduce set_special_state()
  kthread, sched/wait: Fix kthread_parkme() completion issue
  kthread, sched/wait: Fix kthread_parkme() wait-loop
  sched/fair: Fix the update of blocked load when newly idle
  stop_machine, sched: Fix migrate_swap() vs. active_balance() deadlock

1 files changed, 15 insertions, 2 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index d4ccea599692..9c33163a6165 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1961,14 +1961,27 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
 			return;
 	}
 
+	set_special_state(TASK_TRACED);
+
 	/*
 	 * We're committing to trapping.  TRACED should be visible before
 	 * TRAPPING is cleared; otherwise, the tracer might fail do_wait().
 	 * Also, transition to TRACED and updates to ->jobctl should be
 	 * atomic with respect to siglock and should be done after the arch
 	 * hook as siglock is released and regrabbed across it.
+	 *
+	 *     TRACER				    TRACEE
+	 *
+	 *     ptrace_attach()
+	 * [L]   wait_on_bit(JOBCTL_TRAPPING)	[S] set_special_state(TRACED)
+	 *     do_wait()
+	 *       set_current_state()                smp_wmb();
+	 *       ptrace_do_wait()
+	 *         wait_task_stopped()
+	 *           task_stopped_code()
+	 * [L]         task_is_traced()		[S] task_clear_jobctl_trapping();
 	 */
-	set_current_state(TASK_TRACED);
+	smp_wmb();
 
 	current->last_siginfo = info;
 	current->exit_code = exit_code;
@@ -2176,7 +2189,7 @@ static bool do_signal_stop(int signr)
 		if (task_participate_group_stop(current))
 			notify = CLD_STOPPED;
 
-		__set_current_state(TASK_STOPPED);
+		set_special_state(TASK_STOPPED);
 		spin_unlock_irq(&current->sighand->siglock);
 
 		/*