linux-kernel - [tip:perf/core] uprobes: Kill write_opcode()->lock_page(new

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Date:	Mon, 30 Jul 2012 07:11:25 -0700
From:	tip-bot for Oleg Nesterov <oleg@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, anton@...hat.com, hpa@...or.com,
	mingo@...nel.org, srikar@...ux.vnet.ibm.com, oleg@...hat.com,
	tglx@...utronix.de
Subject: [tip:perf/core] uprobes: Kill write_opcode()->lock_page(new_page)

Commit-ID:  089ba999dc881a7549d97c55ac9e0052d061867d
Gitweb:     http://git.kernel.org/tip/089ba999dc881a7549d97c55ac9e0052d061867d
Author:     Oleg Nesterov <oleg@...hat.com>
AuthorDate: Sun, 29 Jul 2012 20:22:18 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 30 Jul 2012 11:27:19 +0200

uprobes: Kill write_opcode()->lock_page(new_page)

write_opcode() does lock_page(new_page) for no reason. Nobody
can see this page until __replace_page() exposes it under ptl
lock, and we do nothing with this page after pte_unmap_unlock().

If nothing else, the similar code in do_wp_page() doesn't lock
the new page for page_add_new_anon_rmap/set_pte_at_notify.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@...hat.com>
Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182218.GA20315@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 6fda799..23c562b7 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -239,9 +239,7 @@ retry:
 	if (ret)
 		goto unlock_out;
 
-	lock_page(new_page);
 	ret = __replace_page(vma, vaddr, old_page, new_page);
-	unlock_page(new_page);
 
 unlock_out:
 	unlock_page(old_page);
--
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