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try a saner locking for pde_opener...

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2013-04-04 16:28:47 -04:00
parent ca469f35a8
commit 05c0ae21c0
3 changed files with 24 additions and 44 deletions
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62
fs/proc/inode.c
View File

@ -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;
}

4
fs/proc/internal.h
View File

@ -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 *);

2
include/linux/proc_fs.h
View File

@ -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 */