linux-kernel - Re: Remaining randconfig objtool warnings, linux-next-20200428

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Message-ID: <20200501122743.GB3762@hirez.programming.kicks-ass.net>
Date:   Fri, 1 May 2020 14:27:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Remaining randconfig objtool warnings, linux-next-20200428

On Thu, Apr 30, 2020 at 07:28:58PM -0500, Josh Poimboeuf wrote:
> On Thu, Apr 30, 2020 at 04:05:07PM +0200, Arnd Bergmann wrote:
> > lib/locking-selftest.o: warning: objtool: locking_selftest()+0x117f: PUSHF stack exhausted
> > lib/locking-selftest.o: warning: objtool: ww_tests()+0x1083: PUSHF stack exhausted
> 
> Peter,
> 
> These functions have a bunch of irqs_disabled() checks, which means a
> bunch of PUSHFs with no POPFs.
> 
> Am I reading it correctly that objtool assumes PUSHF is always paired
> with POPF?  irqs_disabled() doesn't do that.

Right, it sorta does. I wonder why this shows up with GCC-10 though, and
not before.

Anyway, the sneaky fix here would be something like this.

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 14f44f59e733..510656c776d9 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -1138,7 +1138,7 @@ static void dotest(void (*testcase_fn)(void), int expected, int lockclass_mask)
 {
 	unsigned long saved_preempt_count = preempt_count();
 
-	WARN_ON(irqs_disabled());
+	lockdep_assert_irqs_enabled();
 
 	testcase_fn();
 	/*