From: Frederic Weisbecker <frederic@kernel.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Paul Burton <paulburton@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"David S . Miller" <davem@davemloft.net>,
Borislav Petkov <bp@alien8.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Andy Lutomirski <luto@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Ralf Baechle <ralf@linux-mips.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Russell King <linux@armlinux.org.uk>
Subject: [PATCH 1/5] x86/entry: Remove _TIF_NOHZ from _TIF_WORK_SYSCALL_ENTRY
Date: Fri, 14 Feb 2020 16:26:11 +0100 [thread overview]
Message-ID: <20200214152615.25447-2-frederic@kernel.org> (raw)
In-Reply-To: <20200214152615.25447-1-frederic@kernel.org>
From: Thomas Gleixner <tglx@linutronix.de>
Evaluating _TIF_NOHZ to decide whether to use the slow syscall entry path
is not only pointless, it's actually counterproductive:
1) Context tracking code is invoked unconditionally before that flag is
evaluated.
2) If the flag is set the slow path is invoked for nothing due to #1
Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
arch/x86/include/asm/thread_info.h | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index cf4327986e98..6cb9d1b0d1e6 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -133,14 +133,10 @@ struct thread_info {
#define _TIF_X32 (1 << TIF_X32)
#define _TIF_FSCHECK (1 << TIF_FSCHECK)
-/*
- * work to do in syscall_trace_enter(). Also includes TIF_NOHZ for
- * enter_from_user_mode()
- */
+/* Work to do before invoking the actual syscall. */
#define _TIF_WORK_SYSCALL_ENTRY \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT | \
- _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \
- _TIF_NOHZ)
+ _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT)
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW_BASE \
--
2.25.0
next prev parent reply other threads:[~2020-02-14 15:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 15:26 [PATCH 0/5] context_tracking: Remove TIF_NOHZ from 3 archs Frederic Weisbecker
2020-02-14 15:26 ` Frederic Weisbecker [this message]
2020-02-14 15:26 ` [PATCH 2/5] context-tracking: Introduce CONFIG_HAVE_TIF_NOHZ Frederic Weisbecker
2020-02-14 15:26 ` [PATCH 3/5] x86: Remove TIF_NOHZ Frederic Weisbecker
2020-02-14 15:26 ` [PATCH 4/5] arm: " Frederic Weisbecker
2020-02-14 15:26 ` [PATCH 5/5] arm64: " Frederic Weisbecker
2020-02-18 8:57 ` Will Deacon
2020-02-18 14:30 ` Frederic Weisbecker
2020-02-20 15:13 ` [GIT PULL] context_tracking: Remove TIF_NOHZ from 3 archs Frederic Weisbecker
2020-02-27 13:23 ` Frederic Weisbecker
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