linux-kernel - [PATCH 2/7 v6] x86/hw-breakpoints: Actually flush thread breakpoints in flush

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Message-Id: <1257694141-5670-3-git-send-email-fweisbec@gmail.com>
Date:	Sun,  8 Nov 2009 16:28:56 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Prasad <prasad@...ux.vnet.ibm.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jan Kiszka <jan.kiszka@....de>,
	Jiri Slaby <jirislaby@...il.com>, Avi Kivity <avi@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Mike Galbraith <efault@....de>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 2/7 v6] x86/hw-breakpoints: Actually flush thread breakpoints in flush_thread().

From: Paul Mundt <lethal@...ux-sh.org>

flush_thread() tries to do a TIF_DEBUG check before calling in to
flush_thread_hw_breakpoint() (which subsequently clears the thread flag),
but for some reason, the x86 code is manually clearing TIF_DEBUG
immediately before the test, so this path will never be taken.

This kills off the erroneous clear_tsk_thread_flag() and lets
flush_thread_hw_breakpoint() actually get invoked.

Presumably folks were getting lucky with testing and the
free_thread_info() -> free_thread_xstate() path was taking care of the
flush there.

Signed-off-by: Paul Mundt <lethal@...ux-sh.org>
Acked-by: "K.Prasad" <prasad@...ux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Alan Stern <stern@...land.harvard.edu>
LKML-Reference: <20091005102306.GA7889@...ux-sh.org>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 arch/x86/kernel/process.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 2275ce5..cf8ee00 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -107,8 +107,6 @@ void flush_thread(void)
 	}
 #endif
 
-	clear_tsk_thread_flag(tsk, TIF_DEBUG);
-
 	if (unlikely(test_tsk_thread_flag(tsk, TIF_DEBUG)))
 		flush_thread_hw_breakpoint(tsk);
 	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
-- 
1.6.2.3

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