linux-kernel - [RESEND PATCH 1/3] uprobes: Remove redundant lock_page/unlock

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Message-ID: <20120601091950.GF24279@linux.vnet.ibm.com>
Date:	Fri, 1 Jun 2012 14:49:50 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Anton Arapov <anton@...hat.com>
Subject: [RESEND PATCH 1/3] uprobes: Remove redundant lock_page/unlock_page

From: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

Since read_opcode() reads from the referenced page and doesnt modify
the page contents nor the page attributes, there is no need to lock
the page.

Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
---
 Modified changelog based on comments from Peter Zijlstra

 kernel/events/uprobes.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 42b21eb..b3f3095 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -315,12 +315,10 @@ static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_
 	if (ret <= 0)
 		return ret;
 
-	lock_page(page);
 	vaddr_new = kmap_atomic(page);
 	vaddr &= ~PAGE_MASK;
 	memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
 	kunmap_atomic(vaddr_new);
-	unlock_page(page);
 
 	put_page(page);
 

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