From 05c0ae21c034a6f7c6f4c0c63a31167ebb4b061f Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 4 Apr 2013 16:28:47 -0400 Subject: [PATCH] try a saner locking for pde_opener... Signed-off-by: Al Viro --- fs/proc/inode.c | 62 ++++++++++++++--------------------------- fs/proc/internal.h | 4 +-- include/linux/proc_fs.h | 2 +- 3 files changed, 24 insertions(+), 44 deletions(-) diff --git a/fs/proc/inode.c b/fs/proc/inode.c index b5b204d6b07f..3b14a45870a9 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -133,67 +133,48 @@ enum {BIAS = -1U<<31}; static inline int use_pde(struct proc_dir_entry *pde) { - int res = 1; - spin_lock(&pde->pde_unload_lock); - if (unlikely(pde->pde_users < 0)) - res = 0; - else - pde->pde_users++; - spin_unlock(&pde->pde_unload_lock); - return res; -} - -static void __pde_users_dec(struct proc_dir_entry *pde) -{ - if (--pde->pde_users == BIAS) - complete(pde->pde_unload_completion); + return atomic_inc_unless_negative(&pde->in_use); } static void unuse_pde(struct proc_dir_entry *pde) { - spin_lock(&pde->pde_unload_lock); - __pde_users_dec(pde); - spin_unlock(&pde->pde_unload_lock); + if (atomic_dec_return(&pde->in_use) == BIAS) + complete(pde->pde_unload_completion); } /* pde is locked */ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo) { - pdeo->count++; - if (!mutex_trylock(&pdeo->mutex)) { + if (pdeo->closing) { /* somebody else is doing that, just wait */ + DECLARE_COMPLETION_ONSTACK(c); + pdeo->c = &c; spin_unlock(&pde->pde_unload_lock); - mutex_lock(&pdeo->mutex); + wait_for_completion(&c); spin_lock(&pde->pde_unload_lock); - WARN_ON(!list_empty(&pdeo->lh)); } else { struct file *file; + pdeo->closing = 1; spin_unlock(&pde->pde_unload_lock); file = pdeo->file; pde->proc_fops->release(file_inode(file), file); spin_lock(&pde->pde_unload_lock); list_del_init(&pdeo->lh); - } - mutex_unlock(&pdeo->mutex); - if (!--pdeo->count) + if (pdeo->c) + complete(pdeo->c); kfree(pdeo); + } } void proc_entry_rundown(struct proc_dir_entry *de) { - spin_lock(&de->pde_unload_lock); - de->pde_users += BIAS; + DECLARE_COMPLETION_ONSTACK(c); /* Wait until all existing callers into module are done. */ - if (de->pde_users != BIAS) { - DECLARE_COMPLETION_ONSTACK(c); - de->pde_unload_completion = &c; - spin_unlock(&de->pde_unload_lock); - - wait_for_completion(de->pde_unload_completion); - - spin_lock(&de->pde_unload_lock); - } + de->pde_unload_completion = &c; + if (atomic_add_return(BIAS, &de->in_use) != BIAS) + wait_for_completion(&c); + spin_lock(&de->pde_unload_lock); while (!list_empty(&de->pde_openers)) { struct pde_opener *pdeo; pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh); @@ -356,7 +337,7 @@ static int proc_reg_open(struct inode *inode, struct file *file) * by hand in remove_proc_entry(). For this, save opener's credentials * for later. */ - pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL); + pdeo = kzalloc(sizeof(struct pde_opener), GFP_KERNEL); if (!pdeo) return -ENOMEM; @@ -370,18 +351,17 @@ static int proc_reg_open(struct inode *inode, struct file *file) if (open) rv = open(inode, file); - spin_lock(&pde->pde_unload_lock); if (rv == 0 && release) { /* To know what to release. */ - mutex_init(&pdeo->mutex); - pdeo->count = 0; pdeo->file = file; /* Strictly for "too late" ->release in proc_reg_release(). */ + spin_lock(&pde->pde_unload_lock); list_add(&pdeo->lh, &pde->pde_openers); + spin_unlock(&pde->pde_unload_lock); } else kfree(pdeo); - __pde_users_dec(pde); - spin_unlock(&pde->pde_unload_lock); + + unuse_pde(pde); return rv; } diff --git a/fs/proc/internal.h b/fs/proc/internal.h index e2fa9345a9a8..46a7e2a7b904 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -153,8 +153,8 @@ int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent, struct pde_opener { struct file *file; struct list_head lh; - int count; /* number of threads in close_pdeo() */ - struct mutex mutex; + int closing; + struct completion *c; }; ssize_t __proc_file_read(struct file *, char __user *, size_t, loff_t *); diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index 947ae7eb63ef..2781e498f709 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -65,7 +65,7 @@ struct proc_dir_entry { void *data; read_proc_t *read_proc; atomic_t count; /* use count */ - int pde_users; /* number of callers into module in progress; */ + atomic_t in_use; /* number of callers into module in progress; */ /* negative -> it's going away RSN */ struct completion *pde_unload_completion; struct list_head pde_openers; /* who did ->open, but not ->release */ -- 2.20.1