linux-kernel - [tip:perf/core] x86/hw-breakpoints: Actually flush thread breakpoints in flush

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Message-ID: <tip-41a48d14f6991020c9bb6b93e289ca5b411ed09a@git.kernel.org>
Date:	Sat, 21 Nov 2009 13:36:38 GMT
From:	tip-bot for Paul Mundt <lethal@...ux-sh.org>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	stern@...land.harvard.edu, lethal@...ux-sh.org, fweisbec@...il.com,
	tglx@...utronix.de, prasad@...ux.vnet.ibm.com, mingo@...e.hu
Subject: [tip:perf/core] x86/hw-breakpoints: Actually flush thread breakpoints in flush_thread().

Commit-ID:  41a48d14f6991020c9bb6b93e289ca5b411ed09a
Gitweb:     http://git.kernel.org/tip/41a48d14f6991020c9bb6b93e289ca5b411ed09a
Author:     Paul Mundt <lethal@...ux-sh.org>
AuthorDate: Mon, 5 Oct 2009 19:23:06 +0900
Committer:  Frederic Weisbecker <fweisbec@...il.com>
CommitDate: Tue, 3 Nov 2009 18:05:44 +0100

x86/hw-breakpoints: Actually flush thread breakpoints in flush_thread().

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));
--
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