linux-kernel - Re: [PATCH 1/2] coresight: cti: Initialize dynamic sysfs attributes

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Message-ID: <20201029191011.GA826513@kroah.com>
Date:   Thu, 29 Oct 2020 20:10:11 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] coresight: cti: Initialize dynamic sysfs attributes

On Thu, Oct 29, 2020 at 10:45:58AM -0600, Mathieu Poirier wrote:
> From: Suzuki K Poulose <suzuki.poulose@....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@...aro.org>
> Tested-by: Leo Yan <leo.yan@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.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;
>  }

Should go to stable kernels too, as the patch this fixes is in 5.7.
I'll add the stable tag here, but feel free to do it yourself next time
:)

thanks,

greg k-h