From 8f1f745331c1b560f53c0d60e55a4f4f43f7cce5 Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Thu, 3 Feb 2011 14:33:15 -0500 Subject: [PATCH] ext4: fix panic on module unload when stopping lazyinit thread https://bugzilla.kernel.org/show_bug.cgi?id=27652 If the lazyinit thread is running, the teardown function ext4_destroy_lazyinit_thread() has problems: ext4_clear_request_list(); while (ext4_li_info->li_task) { wake_up(&ext4_li_info->li_wait_daemon); wait_event(ext4_li_info->li_wait_task, ext4_li_info->li_task == NULL); } Clearing the request list will cause the thread to exit and free ext4_li_info, so then we're waiting on something which is getting freed. Fix this up by making the thread respond to kthread_stop, and exit, without the need to wait for that exit in some other homegrown way. Cc: stable@kernel.org Reported-and-Tested-by: Tao Ma Signed-off-by: Eric Sandeen Signed-off-by: "Theodore Ts'o" --- fs/ext4/super.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 48ce561fafac..3d8cf2cab379 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -77,6 +77,7 @@ static struct dentry *ext4_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data); static void ext4_destroy_lazyinit_thread(void); static void ext4_unregister_li_request(struct super_block *sb); +static void ext4_clear_request_list(void); #if !defined(CONFIG_EXT3_FS) && !defined(CONFIG_EXT3_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23) static struct file_system_type ext3_fs_type = { @@ -2716,6 +2717,8 @@ static void ext4_unregister_li_request(struct super_block *sb) mutex_unlock(&ext4_li_info->li_list_mtx); } +static struct task_struct *ext4_lazyinit_task; + /* * This is the function where ext4lazyinit thread lives. It walks * through the request list searching for next scheduled filesystem. @@ -2784,6 +2787,10 @@ cont_thread: if (time_before(jiffies, next_wakeup)) schedule(); finish_wait(&eli->li_wait_daemon, &wait); + if (kthread_should_stop()) { + ext4_clear_request_list(); + goto exit_thread; + } } exit_thread: @@ -2808,6 +2815,7 @@ exit_thread: wake_up(&eli->li_wait_task); kfree(ext4_li_info); + ext4_lazyinit_task = NULL; ext4_li_info = NULL; mutex_unlock(&ext4_li_mtx); @@ -2830,11 +2838,10 @@ static void ext4_clear_request_list(void) static int ext4_run_lazyinit_thread(void) { - struct task_struct *t; - - t = kthread_run(ext4_lazyinit_thread, ext4_li_info, "ext4lazyinit"); - if (IS_ERR(t)) { - int err = PTR_ERR(t); + ext4_lazyinit_task = kthread_run(ext4_lazyinit_thread, + ext4_li_info, "ext4lazyinit"); + if (IS_ERR(ext4_lazyinit_task)) { + int err = PTR_ERR(ext4_lazyinit_task); ext4_clear_request_list(); del_timer_sync(&ext4_li_info->li_timer); kfree(ext4_li_info); @@ -2985,16 +2992,10 @@ static void ext4_destroy_lazyinit_thread(void) * If thread exited earlier * there's nothing to be done. */ - if (!ext4_li_info) + if (!ext4_li_info || !ext4_lazyinit_task) return; - ext4_clear_request_list(); - - while (ext4_li_info->li_task) { - wake_up(&ext4_li_info->li_wait_daemon); - wait_event(ext4_li_info->li_wait_task, - ext4_li_info->li_task == NULL); - } + kthread_stop(ext4_lazyinit_task); } static int ext4_fill_super(struct super_block *sb, void *data, int silent) -- 2.20.1