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SubjectRe: [Patch] sysfs: add lockdep class support to s_active
Amerigo Wang wrote:
> Recently we met a lockdep warning from sysfs during s2ram or cpu hotplug.
> As reported by several people, it is something like:
>
> [ 6967.926563] ACPI: Preparing to enter system sleep state S3
> [ 6967.956156] Disabling non-boot CPUs ...
> [ 6967.970401]
> [ 6967.970408] =============================================
> [ 6967.970419] [ INFO: possible recursive locking detected ]
> [ 6967.970431] 2.6.33-rc2-git6 #27
> [ 6967.970439] ---------------------------------------------
> [ 6967.970450] pm-suspend/22147 is trying to acquire lock:
> [ 6967.970460] (s_active){++++.+}, at: [<c10d2941>]
> sysfs_hash_and_remove+0x3d/0x4f
> [ 6967.970493]
> [ 6967.970497] but task is already holding lock:
> [ 6967.970506] (s_active){++++.+}, at: [<c10d4110>]
> sysfs_get_active_two+0x16/0x36
> [...]
>
> Eric already provides a patch for this[1], but it still can't fix the
> problem. Based on his work and Peter's suggestion, I write this patch,
> hopefully we can fix the warning completely.
>
> This patch put sysfs s_active into two classes, one is for PM, the other
> is for the rest, so lockdep will distinguish them.
>
> 1. http://lkml.org/lkml/2010/1/10/282
>
>
> Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Reported-by: Miles Lane <miles.lane@gmail.com>
> Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
> Signed-off-by: WANG Cong <amwang@redhat.com>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@suse.de>
>
>
> ---
> diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> index dc30d9e..72a8d0b 100644
> --- a/fs/sysfs/file.c
> +++ b/fs/sysfs/file.c
> @@ -24,6 +24,8 @@
>
> #include "sysfs.h"
>
> +static struct lock_class_key sysfs_classes[SYSFS_NR_CLASSES];
> +
> /* used in crash dumps to help with debugging */
> static char last_sysfs_file[PATH_MAX];
> void sysfs_printk_last_file(void)
> @@ -504,11 +506,16 @@ int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
> struct sysfs_addrm_cxt acxt;
> struct sysfs_dirent *sd;
> int rc;
> + int class;
>
> sd = sysfs_new_dirent(attr->name, mode, type);
> if (!sd)
> return -ENOMEM;
> sd->s_attr.attr = (void *)attr;
> + class = SYSFS_ATTR_NORMAL;
> + if (sysfs_type(sd) == SYSFS_KOBJ_ATTR)
> + class = sd->s_attr.attr->class;
> + lockdep_set_class(&sd->s_active, &sysfs_classes[class]);
>

Oops! I missed one part, please ignore this patch...


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