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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Robin Murphy <robin.murphy@arm.com>,
        Will Deacon <will@kernel.org>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.16 0284/1039] perf/arm-cmn: Fix CPU hotplug unregistration
Date:   Mon, 24 Jan 2022 19:34:33 +0100
Message-Id: <20220124184134.829380525@linuxfoundation.org>
In-Reply-To: <20220124184125.121143506@linuxfoundation.org>
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From: Robin Murphy <robin.murphy@arm.com>

[ Upstream commit 56c7c6eaf3eb8ac1ec40d56096c0f2b27250da5f ]

Attempting to migrate the PMU context after we've unregistered the PMU
device, or especially if we never successfully registered it in the
first place, is a woefully bad idea. It's also fundamentally pointless
anyway. Make sure to unregister an instance from the hotplug handler
*without* invoking the teardown callback.

Fixes: 0ba64770a2f2 ("perf: Add Arm CMN-600 PMU driver")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/2c221d745544774e4b07583b65b5d4d94f7e0fe4.1638530442.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/perf/arm-cmn.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index bc3cba5f8c5dc..400eb7f579dce 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1561,7 +1561,8 @@ static int arm_cmn_probe(struct platform_device *pdev)
 
 	err = perf_pmu_register(&cmn->pmu, name, -1);
 	if (err)
-		cpuhp_state_remove_instance(arm_cmn_hp_state, &cmn->cpuhp_node);
+		cpuhp_state_remove_instance_nocalls(arm_cmn_hp_state, &cmn->cpuhp_node);
+
 	return err;
 }
 
@@ -1572,7 +1573,7 @@ static int arm_cmn_remove(struct platform_device *pdev)
 	writel_relaxed(0, cmn->dtc[0].base + CMN_DT_DTC_CTL);
 
 	perf_pmu_unregister(&cmn->pmu);
-	cpuhp_state_remove_instance(arm_cmn_hp_state, &cmn->cpuhp_node);
+	cpuhp_state_remove_instance_nocalls(arm_cmn_hp_state, &cmn->cpuhp_node);
 	return 0;
 }
 
-- 
2.34.1