linux-kernel - [tip:perf/core] x86/fpu: Turn WARN_ON() in context switch into WARN_ON

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Message-ID: <tip-6061efb6ee6fc891498a23994a4d0a5e2a52c059@git.kernel.org>
Date:   Mon, 24 Apr 2017 14:00:58 -0700
From:   tip-bot for Andi Kleen <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     ak@...ux.intel.com, hpa@...or.com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: [tip:perf/core] x86/fpu: Turn WARN_ON() in context switch into
 WARN_ON_FPU()

Commit-ID:  6061efb6ee6fc891498a23994a4d0a5e2a52c059
Gitweb:     http://git.kernel.org/tip/6061efb6ee6fc891498a23994a4d0a5e2a52c059
Author:     Andi Kleen <ak@...ux.intel.com>
AuthorDate: Tue, 28 Mar 2017 23:26:05 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 31 Mar 2017 11:20:05 +0200

x86/fpu: Turn WARN_ON() in context switch into WARN_ON_FPU()

copy_xregs_to_kernel checks if the alternatives have been already
patched.

This WARN_ON() is always executed in every context switch.

All the other checks in fpu internal.h are WARN_ON_FPU(), but
this one is plain WARN_ON(). I assume it was forgotten to switch it.

So switch it to WARN_ON_FPU() too to avoid some unnecessary code
in the context switch, and a potentially expensive cache line miss for the
global variable.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20170329062605.4970-1-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/fpu/internal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index bbee00aa..8044dc1 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -350,7 +350,7 @@ static inline void copy_xregs_to_kernel(struct xregs_state *xstate)
 	u32 hmask = mask >> 32;
 	int err;
 
-	WARN_ON(!alternatives_patched);
+	WARN_ON_FPU(!alternatives_patched);
 
 	XSTATE_XSAVE(xstate, lmask, hmask, err);