linux-kernel - [PATCH] powerpc/xmon: Fix data-breakpoint

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Date:   Tue, 22 Nov 2016 14:55:59 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:     mpe@...erman.id.au
Cc:     benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        peterz@...radead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, naveen.n.rao@...ux.vnet.ibm.com,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: [PATCH] powerpc/xmon: Fix data-breakpoint

Xmon data-breakpoint feature is broken.

Whenever there is a watchpoint match occurs, hw_breakpoint_handler will
be called by do_break via notifier chains mechanism. If watchpoint is
registered by xmon, hw_breakpoint_handler won't find any associated
perf_event and returns immediately with NOTIFY_STOP. Similarly, do_break
also returns without notifying to xmon.

Solve this by returning NOTIFY_DONE when hw_breakpoint_handler does not
find any perf_event associated with matched watchpoint.

Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
---
 arch/powerpc/kernel/hw_breakpoint.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 03d089b..469d86d 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -228,8 +228,10 @@ int hw_breakpoint_handler(struct die_args *args)
 	rcu_read_lock();

 	bp = __this_cpu_read(bp_per_reg);
-	if (!bp)
+	if (!bp) {
+		rc = NOTIFY_DONE;
 		goto out;
+	}
 	info = counter_arch_bp(bp);

 	/*
-- 
1.8.3.1