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From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     gregkh@linuxfoundation.org
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] coresight: cti: Initialize dynamic sysfs attributes
Date:   Thu, 29 Oct 2020 10:45:58 -0600
Message-Id: <20201029164559.1268531-2-mathieu.poirier@linaro.org>
In-Reply-To: <20201029164559.1268531-1-mathieu.poirier@linaro.org>
References: <20201029164559.1268531-1-mathieu.poirier@linaro.org>
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From: Suzuki K Poulose <suzuki.poulose@arm.com>

With LOCKDEP enabled, CTI driver triggers the following splat due
to uninitialized lock class for dynamically allocated attribute
objects.

[    5.372901] coresight etm0: CPU0: ETM v4.0 initialized
[    5.376694] coresight etm1: CPU1: ETM v4.0 initialized
[    5.380785] coresight etm2: CPU2: ETM v4.0 initialized
[    5.385851] coresight etm3: CPU3: ETM v4.0 initialized
[    5.389808] BUG: key ffff00000564a798 has not been registered!
[    5.392456] ------------[ cut here ]------------
[    5.398195] DEBUG_LOCKS_WARN_ON(1)
[    5.398233] WARNING: CPU: 1 PID: 32 at kernel/locking/lockdep.c:4623 lockdep_init_map_waits+0x14c/0x260
[    5.406149] Modules linked in:
[    5.415411] CPU: 1 PID: 32 Comm: kworker/1:1 Not tainted 5.9.0-12034-gbbe85027ce80 #51
[    5.418553] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
[    5.426453] Workqueue: events amba_deferred_retry_func
[    5.433299] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
[    5.438252] pc : lockdep_init_map_waits+0x14c/0x260
[    5.444410] lr : lockdep_init_map_waits+0x14c/0x260
[    5.449007] sp : ffff800012bbb720
...

[    5.531561] Call trace:
[    5.536847]  lockdep_init_map_waits+0x14c/0x260
[    5.539027]  __kernfs_create_file+0xa8/0x1c8
[    5.543539]  sysfs_add_file_mode_ns+0xd0/0x208
[    5.548054]  internal_create_group+0x118/0x3c8
[    5.552307]  internal_create_groups+0x58/0xb8
[    5.556733]  sysfs_create_groups+0x2c/0x38
[    5.561160]  device_add+0x2d8/0x768
[    5.565148]  device_register+0x28/0x38
[    5.568537]  coresight_register+0xf8/0x320
[    5.572358]  cti_probe+0x1b0/0x3f0

...

Fix this by initializing the attributes when they are allocated.

Fixes: 3c5597e39812 ("coresight: cti: Add connection information to sysfs")
Reported-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Leo Yan <leo.yan@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-cti-sysfs.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
index 392757f3a019..7ff7e7780bbf 100644
--- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
@@ -1065,6 +1065,13 @@ static int cti_create_con_sysfs_attr(struct device *dev,
 	}
 	eattr->var = con;
 	con->con_attrs[attr_idx] = &eattr->attr.attr;
+	/*
+	 * Initialize the dynamically allocated attribute
+	 * to avoid LOCKDEP splat. See include/linux/sysfs.h
+	 * for more details.
+	 */
+	sysfs_attr_init(con->con_attrs[attr_idx]);
+
 	return 0;
 }
 
-- 
2.25.1