linux-kernel - [PATCH -tip] x86: hw-breakpoints: Actually flush thread breakpoints in flush

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Message-ID: <20091005102306.GA7889@linux-sh.org>
Date:	Mon, 5 Oct 2009 19:23:06 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	"K.Prasad" <prasad@...ux.vnet.ibm.com>, Ingo Molnar <mingo@...e.hu>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH -tip] x86: hw-breakpoints: Actually flush thread breakpoints in flush_thread().

[ I noticed this whilst hacking up SH support, applies to the current
  tracing/hw-breakpoints topic branch. ]

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>

---

 arch/x86/kernel/process.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1092a1a..c62f647 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -110,8 +110,6 @@ 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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