Patch "rcu: Remove spurious instrumentation_end() in rcu_nmi_enter()" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    rcu: Remove spurious instrumentation_end() in rcu_nmi_enter()

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rcu-remove-spurious-instrumentation_end-in-rcu_nmi_e.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9c6d2f7c3117da380dd98d8b0b11bbcfa5113d14
Author: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Date:   Mon Jan 11 09:08:59 2021 +0800

    rcu: Remove spurious instrumentation_end() in rcu_nmi_enter()
    
    [ Upstream commit 6494ccb93271bee596a12db32ff44867d5be2321 ]
    
    In rcu_nmi_enter(), there is an erroneous instrumentation_end() in the
    second branch of the "if" statement.  Oddly enough, "objtool check -f
    vmlinux.o" fails to complain because it is unable to correctly cover
    all cases.  Instead, objtool visits the third branch first, which marks
    following trace_rcu_dyntick() as visited.  This commit therefore removes
    the spurious instrumentation_end().
    
    Fixes: 04b25a495bd6 ("rcu: Mark rcu_nmi_enter() call to rcu_cleanup_after_idle() noinstr")
    Reported-by Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
    Signed-off-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
    Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8a5cc76ecac9..61e250cdd7c9 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1019,7 +1019,6 @@ noinstr void rcu_nmi_enter(void)
 	} else if (!in_nmi()) {
 		instrumentation_begin();
 		rcu_irq_enter_check_tick();
-		instrumentation_end();
 	} else  {
 		instrumentation_begin();
 	}