linux-kernel - [PATCH 05/13] perf/hw_breakpoint: Enable breakpoint in modify_user_hw

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Date:   Mon,  3 Sep 2018 11:52:16 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Clark Williams <williams@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        David Ahern <dsahern@...il.com>,
        Milind Chabbi <chabbi.milind@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 05/13] perf/hw_breakpoint: Enable breakpoint in modify_user_hw_breakpoint

From: Jiri Olsa <jolsa@...nel.org>

Currently we enable the breakpoint back only if the breakpoint
modification was successful. If it fails we can leave the breakpoint in
disabled state with attr->disabled == 0.

We can safely enable the breakpoint back for both the fail and success
paths by checking the bp->attr.disabled, which either holds the new
'requested' disabled state or the original breakpoint state.

Suggested-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
Acked-by: Frederic Weisbecker <frederic@...nel.org>
Acked-by: Oleg Nesterov <oleg@...hat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Milind Chabbi <chabbi.milind@...il.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20180827091228.2878-5-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 kernel/events/hw_breakpoint.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 3e560d7609fd..d6b56180827c 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -523,13 +523,11 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att
 		perf_event_disable(bp);
 
 	err = modify_user_hw_breakpoint_check(bp, attr, false);
-	if (err)
-		return err;
 
-	if (!attr->disabled)
+	if (!bp->attr.disabled)
 		perf_event_enable(bp);
 
-	return 0;
+	return err;
 }
 EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
 
-- 
2.14.4