From fe7b5641611f55c41d798f2a48d1b2af9ace5b1b Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Sat, 29 Sep 2012 21:56:57 +0200
Subject: [PATCH] --- yaml --- r: 334766 b: refs/heads/master c:
 142b18ddc81439acda4bc4231b291e99fe67d507 h: refs/heads/master v: v3

---
 [refs]                        | 2 +-
 trunk/kernel/events/uprobes.c | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 4cca67dc9eb3..196b88c3509a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 076a365b3da99b68c5d58e394714d0611f1fa002
+refs/heads/master: 142b18ddc81439acda4bc4231b291e99fe67d507
diff --git a/trunk/kernel/events/uprobes.c b/trunk/kernel/events/uprobes.c
index a1b466d17c17..c718fef28617 100644
--- a/trunk/kernel/events/uprobes.c
+++ b/trunk/kernel/events/uprobes.c
@@ -596,6 +596,7 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
 		BUG_ON((uprobe->offset & ~PAGE_MASK) +
 				UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
 
+		smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
 		uprobe->flags |= UPROBE_COPY_INSN;
 	}
 
@@ -1436,6 +1437,14 @@ static void handle_swbp(struct pt_regs *regs)
 		}
 		return;
 	}
+	/*
+	 * TODO: move copy_insn/etc into _register and remove this hack.
+	 * After we hit the bp, _unregister + _register can install the
+	 * new and not-yet-analyzed uprobe at the same address, restart.
+	 */
+	smp_rmb(); /* pairs with wmb() in install_breakpoint() */
+	if (unlikely(!(uprobe->flags & UPROBE_COPY_INSN)))
+		goto restart;
 
 	utask = current->utask;
 	if (!utask) {