From 54d71145a4548330313ca664a4a009772fe8b7dd Mon Sep 17 00:00:00 2001 From: Mika Westerberg Date: Wed, 20 Nov 2013 11:56:35 +0200 Subject: sysfs: handle duplicate removal attempts in sysfs_remove_group() Commit bcdde7e221a8 (sysfs: make __sysfs_remove_dir() recursive) changed the behavior so that directory removals will be done recursively. This means that the sysfs group might already be removed if its parent directory has been removed. The current code outputs warnings similar to following log snippet when it detects that there is no group for the given kobject: WARNING: CPU: 0 PID: 4 at fs/sysfs/group.c:214 sysfs_remove_group+0xc6/0xd0() sysfs group ffffffff81c6f1e0 not found for kobject 'host7' Modules linked in: CPU: 0 PID: 4 Comm: kworker/0:0 Not tainted 3.12.0+ #13 Hardware name: /D33217CK, BIOS GKPPT10H.86A.0042.2013.0422.1439 04/22/2013 Workqueue: kacpi_hotplug acpi_hotplug_work_fn 0000000000000009 ffff8801002459b0 ffffffff817daab1 ffff8801002459f8 ffff8801002459e8 ffffffff810436b8 0000000000000000 ffffffff81c6f1e0 ffff88006d440358 ffff88006d440188 ffff88006e8b4c28 ffff880100245a48 Call Trace: [] dump_stack+0x45/0x56 [] warn_slowpath_common+0x78/0xa0 [] warn_slowpath_fmt+0x47/0x50 [] ? sysfs_get_dirent_ns+0x49/0x70 [] sysfs_remove_group+0xc6/0xd0 [] dpm_sysfs_remove+0x3e/0x50 [] device_del+0x40/0x1b0 [] device_unregister+0xd/0x20 [] scsi_remove_host+0xba/0x110 [] ata_host_detach+0xc6/0x100 [] ata_pci_remove_one+0x18/0x20 [] pci_device_remove+0x28/0x60 [] __device_release_driver+0x64/0xd0 [] device_release_driver+0x1e/0x30 [] bus_remove_device+0xf7/0x140 [] device_del+0x121/0x1b0 [] pci_stop_bus_device+0x94/0xa0 [] pci_stop_bus_device+0x3b/0xa0 [] pci_stop_bus_device+0x3b/0xa0 [] pci_stop_and_remove_bus_device+0xd/0x20 [] trim_stale_devices+0x73/0xe0 [] trim_stale_devices+0xbb/0xe0 [] trim_stale_devices+0xbb/0xe0 [] acpiphp_check_bridge+0x7e/0xd0 [] hotplug_event+0xcd/0x160 [] hotplug_event_work+0x25/0x60 [] acpi_hotplug_work_fn+0x17/0x22 [] process_one_work+0x17a/0x430 [] worker_thread+0x119/0x390 [] ? manage_workers.isra.25+0x2a0/0x2a0 [] kthread+0xcd/0xf0 [] ? kthread_create_on_node+0x180/0x180 [] ret_from_fork+0x7c/0xb0 [] ? kthread_create_on_node+0x180/0x180 On this particular machine I see ~16 of these message during Thunderbolt hot-unplug. Fix this in similar way that was done for sysfs_remove_one() by checking if the parent directory has already been removed and bailing out early. Signed-off-by: Mika Westerberg Acked-by: Rafael J. Wysocki Acked-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/group.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c index 1898a10e38ce..3796afdff40c 100644 --- a/fs/sysfs/group.c +++ b/fs/sysfs/group.c @@ -206,6 +206,15 @@ void sysfs_remove_group(struct kobject *kobj, struct sysfs_dirent *dir_sd = kobj->sd; struct sysfs_dirent *sd; + /* + * Sysfs directories are now removed recursively by + * sysfs_remove_dir(). This means that the function can be called + * for a group whose sysfs entry is already removed. In that case + * all its groups are guaranteed to be already removed. + */ + if (dir_sd->s_flags & SYSFS_FLAG_REMOVED) + return; + if (grp->name) { sd = sysfs_get_dirent(dir_sd, grp->name); if (!sd) { -- cgit v1.2.3 From 027a485d12e089314360d459b8d847104dd28702 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sun, 17 Nov 2013 11:17:36 +0900 Subject: sysfs: use a separate locking class for open files depending on mmap The following two commits implemented mmap support in the regular file path and merged bin file support into the regular path. 73d9714627ad ("sysfs: copy bin mmap support from fs/sysfs/bin.c to fs/sysfs/file.c") 3124eb1679b2 ("sysfs: merge regular and bin file handling") After the merge, the following commands trigger a spurious lockdep warning. "test-mmap-read" simply mmaps the file and dumps the content. $ cat /sys/block/sda/trace/act_mask $ test-mmap-read /sys/devices/pci0000\:00/0000\:00\:03.0/resource0 4096 ====================================================== [ INFO: possible circular locking dependency detected ] 3.12.0-work+ #378 Not tainted ------------------------------------------------------- test-mmap-read/567 is trying to acquire lock: (&of->mutex){+.+.+.}, at: [] sysfs_bin_mmap+0x4f/0x120 but task is already holding lock: (&mm->mmap_sem){++++++}, at: [] vm_mmap_pgoff+0x49/0xa0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&mm->mmap_sem){++++++}: ... -> #2 (sr_mutex){+.+.+.}: ... -> #1 (&bdev->bd_mutex){+.+.+.}: ... -> #0 (&of->mutex){+.+.+.}: ... other info that might help us debug this: Chain exists of: &of->mutex --> sr_mutex --> &mm->mmap_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&mm->mmap_sem); lock(sr_mutex); lock(&mm->mmap_sem); lock(&of->mutex); *** DEADLOCK *** 1 lock held by test-mmap-read/567: #0: (&mm->mmap_sem){++++++}, at: [] vm_mmap_pgoff+0x49/0xa0 stack backtrace: CPU: 3 PID: 567 Comm: test-mmap-read Not tainted 3.12.0-work+ #378 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 ffffffff81ed41a0 ffff880009441bc8 ffffffff81611ad2 ffffffff81eccb80 ffff880009441c08 ffffffff8160f215 ffff880009441c60 ffff880009c75208 0000000000000000 ffff880009c751e0 ffff880009c75208 ffff880009c74ac0 Call Trace: [] dump_stack+0x4e/0x7a [] print_circular_bug+0x2b0/0x2bf [] __lock_acquire+0x1a3a/0x1e60 [] lock_acquire+0x9a/0x1d0 [] mutex_lock_nested+0x67/0x3f0 [] sysfs_bin_mmap+0x4f/0x120 [] mmap_region+0x3b3/0x5b0 [] do_mmap_pgoff+0x34e/0x3d0 [] vm_mmap_pgoff+0x6a/0xa0 [] SyS_mmap_pgoff+0xbe/0x250 [] SyS_mmap+0x22/0x30 [] system_call_fastpath+0x16/0x1b This happens because one file nests sr_mutex, which nests mm->mmap_sem under it, under of->mutex while mmap implementation naturally nests of->mutex under mm->mmap_sem. The warning is false positive as of->mutex is per open-file and the two paths belong to two different files. This warning didn't trigger before regular and bin file supports were merged because only bin file supported mmap and the other side of locking happened only on regular files which used equivalent but separate locking. It'd be best if we give separate locking classes per file but we can't easily do that. Let's differentiate on ->mmap() for now. Later we'll add explicit file operations struct and can add per-ops lockdep key there. Signed-off-by: Tejun Heo Reported-by: Dave Jones Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/file.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 79b5da2acbe1..b94f93685093 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -609,7 +609,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file) struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata; struct kobject *kobj = attr_sd->s_parent->s_dir.kobj; struct sysfs_open_file *of; - bool has_read, has_write; + bool has_read, has_write, has_mmap; int error = -EACCES; /* need attr_sd for attr and ops, its parent for kobj */ @@ -621,6 +621,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file) has_read = battr->read || battr->mmap; has_write = battr->write || battr->mmap; + has_mmap = battr->mmap; } else { const struct sysfs_ops *ops = sysfs_file_ops(attr_sd); @@ -632,6 +633,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file) has_read = ops->show; has_write = ops->store; + has_mmap = false; } /* check perms and supported operations */ @@ -649,7 +651,23 @@ static int sysfs_open_file(struct inode *inode, struct file *file) if (!of) goto err_out; - mutex_init(&of->mutex); + /* + * The following is done to give a different lockdep key to + * @of->mutex for files which implement mmap. This is a rather + * crude way to avoid false positive lockdep warning around + * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and + * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under + * which mm->mmap_sem nests, while holding @of->mutex. As each + * open file has a separate mutex, it's okay as long as those don't + * happen on the same file. At this point, we can't easily give + * each file a separate locking class. Let's differentiate on + * whether the file has mmap or not for now. + */ + if (has_mmap) + mutex_init(&of->mutex); + else + mutex_init(&of->mutex); + of->sd = attr_sd; of->file = file; -- cgit v1.2.3 From 81440e73744446adbe5b5d1f19460203d275028f Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Wed, 27 Nov 2013 09:44:55 -0800 Subject: Revert "sysfs: handle duplicate removal attempts in sysfs_remove_group()" This reverts commit 54d71145a4548330313ca664a4a009772fe8b7dd. The root cause of these "inverted" sysfs removals have now been found, so there is no need for this patch. Keep this functionality around so that this type of error doesn't show up in driver code again. Cc: Mika Westerberg Cc: Rafael J. Wysocki Cc: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/group.c | 9 --------- 1 file changed, 9 deletions(-) diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c index 3796afdff40c..1898a10e38ce 100644 --- a/fs/sysfs/group.c +++ b/fs/sysfs/group.c @@ -206,15 +206,6 @@ void sysfs_remove_group(struct kobject *kobj, struct sysfs_dirent *dir_sd = kobj->sd; struct sysfs_dirent *sd; - /* - * Sysfs directories are now removed recursively by - * sysfs_remove_dir(). This means that the function can be called - * for a group whose sysfs entry is already removed. In that case - * all its groups are guaranteed to be already removed. - */ - if (dir_sd->s_flags & SYSFS_FLAG_REMOVED) - return; - if (grp->name) { sd = sysfs_get_dirent(dir_sd, grp->name); if (!sd) { -- cgit v1.2.3