From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933455Ab0BEHJ4 (ORCPT ); Fri, 5 Feb 2010 02:09:56 -0500 Received: from mail-pz0-f189.google.com ([209.85.222.189]:43354 "EHLO mail-pz0-f189.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933247Ab0BEHJy convert rfc822-to-8bit (ORCPT ); Fri, 5 Feb 2010 02:09:54 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=i9MGrTQwAYoZ6R2/daUQIXj0270xNuds5JfC5/lmXPKiS130Wv4/Yd3GfHhstM4UUX MKRuj+m31iOkHAg1qoZ6b7PgpzMi4bLt88dMnzeEgXgce7LU3lyw+73CMUr4AlQJ5LSz zMGblR47z6kc9qyCyWmqXeqxl485vqkfitWSM= MIME-Version: 1.0 In-Reply-To: <20100205064622.4141.72867.sendpatchset@localhost.localdomain> References: <20100205064622.4141.72867.sendpatchset@localhost.localdomain> Date: Fri, 5 Feb 2010 15:09:49 +0800 Message-ID: <7b6bb4a51002042309v3ca1dd0p60b9dbcacdafaee6@mail.gmail.com> Subject: Re: [Patch v2] sysfs: add lockdep class support to s_active From: Xiaotian Feng To: Amerigo Wang Cc: linux-kernel@vger.kernel.org, Tejun Heo , Greg Kroah-Hartman , Peter Zijlstra , "Eric W. Biederman" , Miles Lane , Heiko Carstens , Benjamin Herrenschmidt , Larry Finger , akpm@linux-foundation.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 5, 2010 at 2:42 PM, 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: [] > sysfs_hash_and_remove+0x3d/0x4f > [ 6967.970493] > [ 6967.970497] but task is already holding lock: > [ 6967.970506]  (s_active){++++.+}, at: [] > 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. I think this patch does not hit the root cause, we have a similiar warning which is not related with PM. Reported by Nick when he's trying to switch evalator. It is reproducable with "echo deadline >/sys/block/sdx/queue/scheduler" while kernel is using cfq. [ INFO: possible recursive locking detected ] 2.6.33-rc6 #1 --------------------------------------------- sh/889 is trying to acquire lock: (s_active){++++.+}, at: [<7820a975>] sysfs_addrm_finish+0x27/0x4e but task is already holding lock: (s_active){++++.+}, at: [<7820ab82>] sysfs_get_active_two+0x18/0x3e other info that might help us debug this: 4 locks held by sh/889: #0: (&buffer->mutex){+.+.+.}, at: [<7820984e>] sysfs_write_file+0x20/0x99 #1: (s_active){++++.+}, at: [<7820ab82>] sysfs_get_active_two+0x18/0x3e #2: (s_active){++++.+}, at: [<7820ab91>] sysfs_get_active_two+0x27/0x3e #3: (&q->sysfs_lock){+.+.+.}, at: [<78289e95>] queue_attr_store+0x2e/0x68 stack backtrace: Pid: 889, comm: sh Not tainted 2.6.33-rc6 #1 Call Trace: [<784a6966>] ? printk+0xf/0x11 [<781752a1>] print_deadlock_bug+0x99/0xa3 [<781753c6>] check_deadlock+0x11b/0x140 [<781763e5>] validate_chain+0x4ec/0x4f9 [<78176a68>] __lock_acquire+0x676/0x6cf [<78176b64>] lock_acquire+0xa3/0xbc [<7820a975>] ? sysfs_addrm_finish+0x27/0x4e [<7820a37a>] sysfs_deactivate+0x6c/0xa4 [<7820a975>] ? sysfs_addrm_finish+0x27/0x4e [<7820a975>] sysfs_addrm_finish+0x27/0x4e [<7820aa3a>] sysfs_remove_dir+0x62/0x72 [<7829d6dd>] kobject_del+0x11/0x32 [<78283406>] __elv_unregister_queue+0x18/0x20 [<78283c66>] elevator_switch+0x6d/0x11b [<78283d92>] elv_iosched_store+0x7e/0x9b [<78289eb8>] queue_attr_store+0x51/0x68 [<78209894>] sysfs_write_file+0x66/0x99 [<781cd460>] vfs_write+0x8a/0x108 [<781cd578>] sys_write+0x3c/0x63 [<78125b90>] sysenter_do_call+0x12/0x36 > > 1. http://lkml.org/lkml/2010/1/10/282 > > > Reported-by: Benjamin Herrenschmidt > Reported-by: Larry Finger > Reported-by: Miles Lane > Reported-by: Heiko Carstens > Signed-off-by: WANG Cong > Cc: Eric W. Biederman > Cc: Peter Zijlstra > Cc: Tejun Heo > Cc: Greg Kroah-Hartman > > --- > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c > index 699f371..d7de269 100644 > --- a/fs/sysfs/dir.c > +++ b/fs/sysfs/dir.c > @@ -354,7 +354,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) > >        atomic_set(&sd->s_count, 1); >        atomic_set(&sd->s_active, 0); > -       sysfs_dirent_init_lockdep(sd); > >        sd->s_name = name; >        sd->s_mode = mode; > diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c > index dc30d9e..97e397a 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_and_name(sd, &sysfs_classes[class], "s_active"); > >        sysfs_addrm_start(&acxt, dir_sd); >        rc = sysfs_add_one(&acxt, sd); > diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h > index cdd9377..dde4d73 100644 > --- a/fs/sysfs/sysfs.h > +++ b/fs/sysfs/sysfs.h > @@ -88,17 +88,6 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd) >        return sd->s_flags & SYSFS_TYPE_MASK; >  } > > -#ifdef CONFIG_DEBUG_LOCK_ALLOC > -#define sysfs_dirent_init_lockdep(sd)                          \ > -do {                                                           \ > -       static struct lock_class_key __key;                     \ > -                                                               \ > -       lockdep_init_map(&sd->dep_map, "s_active", &__key, 0);  \ > -} while(0) > -#else > -#define sysfs_dirent_init_lockdep(sd) do {} while(0) > -#endif > - >  /* >  * Context structure to be used while adding/removing nodes. >  */ > diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h > index cfa8308..2b91b74 100644 > --- a/include/linux/sysfs.h > +++ b/include/linux/sysfs.h > @@ -20,6 +20,12 @@ >  struct kobject; >  struct module; > > +enum sysfs_attr_lock_class { > +       SYSFS_ATTR_NORMAL, > +       SYSFS_ATTR_PM_CONTROL, > +       SYSFS_NR_CLASSES, > +}; > + >  /* FIXME >  * The *owner field is no longer used. >  * x86 tree has been cleaned up. The owner > @@ -29,6 +35,7 @@ struct attribute { >        const char              *name; >        struct module           *owner; >        mode_t                  mode; > +       enum sysfs_attr_lock_class      class; >  }; > >  struct attribute_group { > diff --git a/kernel/power/power.h b/kernel/power/power.h > index 46c5a26..67a6fe7 100644 > --- a/kernel/power/power.h > +++ b/kernel/power/power.h > @@ -54,13 +54,14 @@ extern int hibernation_platform_enter(void); >  extern int pfn_is_nosave(unsigned long); > >  #define power_attr(_name) \ > -static struct kobj_attribute _name##_attr = {  \ > -       .attr   = {                             \ > -               .name = __stringify(_name),     \ > -               .mode = 0644,                   \ > -       },                                      \ > -       .show   = _name##_show,                 \ > -       .store  = _name##_store,                \ > +static struct kobj_attribute _name##_attr = {          \ > +       .attr   = {                                     \ > +               .name = __stringify(_name),             \ > +               .mode = 0644,                           \ > +               .class = SYSFS_ATTR_PM_CONTROL,         \ > +       },                                              \ > +       .show   = _name##_show,                         \ > +       .store  = _name##_store,                        \ >  } > >  /* Preferred image size in bytes (default 500 MB) */ > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html > Please read the FAQ at  http://www.tux.org/lkml/ >