Upgrade to 4.4.50-rt62

The current kernel is based on rt kernel v4.4.6-rt14. We will upgrade it
to 4.4.50-rt62.
The command to achieve it is:
a) Clone a git repo from
git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git

b) Get the diff between this two changesets:
git diff 640eca2901f3435e616157b11379d3223a44b391
705619beeea1b0b48219a683fd1a901a86fdaf5e

where the two commits are:
[yjiang5@jnakajim-build linux-stable-rt]$ git show --oneline --name-only
640eca2901f3435e616157b11379d3223a44b391
640eca2901f3 v4.4.6-rt14
localversion-rt
[yjiang5@jnakajim-build linux-stable-rt]$ git show --oneline --name-only
705619beeea1b0b48219a683fd1a901a86fdaf5e
705619beeea1 Linux 4.4.50-rt62
localversion-rt

c) One patch has been backported thus revert the patch before applying.

 filterdiff -p1 -x scripts/package/Makefile
~/tmp/v4.4.6-rt14-4.4.50-rt62.diff  |patch -p1 --dry-run

Upstream status: backport

Change-Id: I244d57a32f6066e5a5b9915f9fbf99e7bbca6e01
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>

1 files changed, 13 insertions, 10 deletions

diff --git a/kernel/arch/x86/entry/common.c b/kernel/arch/x86/entry/common.c
index 3ec240f39..75a301b6a 100644
--- a/kernel/arch/x86/entry/common.c
+++ b/kernel/arch/x86/entry/common.c
@@ -275,6 +275,7 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
 /* Called with IRQs disabled. */
 __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
 {
+	struct thread_info *ti = pt_regs_to_thread_info(regs);
 	u32 cached_flags;
 
 	if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled()))
@@ -282,12 +283,22 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
 
 	lockdep_sys_exit();
 
-	cached_flags =
-		READ_ONCE(pt_regs_to_thread_info(regs)->flags);
+	cached_flags = READ_ONCE(ti->flags);
 
 	if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
 		exit_to_usermode_loop(regs, cached_flags);
 
+#ifdef CONFIG_COMPAT
+	/*
+	 * Compat syscalls set TS_COMPAT.  Make sure we clear it before
+	 * returning to user mode.  We need to clear it *after* signal
+	 * handling, because syscall restart has a fixup for compat
+	 * syscalls.  The fixup is exercised by the ptrace_syscall_32
+	 * selftest.
+	 */
+	ti->status &= ~TS_COMPAT;
+#endif
+
 	user_enter();
 }
 
@@ -339,14 +350,6 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs)
 	if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
 		syscall_slow_exit_work(regs, cached_flags);
 
-#ifdef CONFIG_COMPAT
-	/*
-	 * Compat syscalls set TS_COMPAT.  Make sure we clear it before
-	 * returning to user mode.
-	 */
-	ti->status &= ~TS_COMPAT;
-#endif
-
 	local_irq_disable();
 	prepare_exit_to_usermode(regs);
 }