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authorAl Viro <viro@zeniv.linux.org.uk>2013-04-04 16:28:47 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2013-04-09 15:16:52 -0400
commit05c0ae21c034a6f7c6f4c0c63a31167ebb4b061f (patch)
tree69c6b35347eeddc49e6ffa2188d4811ce9633c4f
parentca469f35a8e9ef12571a4b80ac6d7fdc0260fb44 (diff)
try a saner locking for pde_opener...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/proc/inode.c62
-rw-r--r--fs/proc/internal.h4
-rw-r--r--include/linux/proc_fs.h2
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 */