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ieee1394: csr1212: proper refcounting
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At least since nodemgr got rid of coarse global locking, accesses to
struct csr1212_keyval's reference counter should be atomic and coupled
with proper barriers.  Also, calls to csr1212_keep_keyval(kv) should
occur before kv is being used.

(We probably should convert refcnt to struct kref, but how to keep
csr1212_destroy_keyval's implementation non-recursively then?)

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
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Stefan Richter committed Oct 16, 2007
1 parent 638d5bb commit 17a19b7
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Showing 3 changed files with 36 additions and 31 deletions.
57 changes: 30 additions & 27 deletions drivers/ieee1394/csr1212.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -218,12 +218,10 @@ static struct csr1212_keyval *csr1212_new_keyval(u8 type, u8 key)
if (!kv)
return NULL;

atomic_set(&kv->refcnt, 1);
kv->key.type = type;
kv->key.id = key;

kv->associate = NULL;
kv->refcnt = 1;

kv->next = NULL;
kv->prev = NULL;
kv->offset = 0;
Expand Down Expand Up @@ -326,12 +324,13 @@ void csr1212_associate_keyval(struct csr1212_keyval *kv,
if (kv->associate)
csr1212_release_keyval(kv->associate);

associate->refcnt++;
csr1212_keep_keyval(associate);
kv->associate = associate;
}

int csr1212_attach_keyval_to_directory(struct csr1212_keyval *dir,
struct csr1212_keyval *kv)
static int __csr1212_attach_keyval_to_directory(struct csr1212_keyval *dir,
struct csr1212_keyval *kv,
bool keep_keyval)
{
struct csr1212_dentry *dentry;

Expand All @@ -341,10 +340,10 @@ int csr1212_attach_keyval_to_directory(struct csr1212_keyval *dir,
if (!dentry)
return -ENOMEM;

if (keep_keyval)
csr1212_keep_keyval(kv);
dentry->kv = kv;

kv->refcnt++;

dentry->next = NULL;
dentry->prev = dir->value.directory.dentries_tail;

Expand All @@ -358,6 +357,12 @@ int csr1212_attach_keyval_to_directory(struct csr1212_keyval *dir,
return CSR1212_SUCCESS;
}

int csr1212_attach_keyval_to_directory(struct csr1212_keyval *dir,
struct csr1212_keyval *kv)
{
return __csr1212_attach_keyval_to_directory(dir, kv, true);
}

#define CSR1212_DESCRIPTOR_LEAF_DATA(kv) \
(&((kv)->value.leaf.data[1]))

Expand Down Expand Up @@ -483,15 +488,18 @@ void csr1212_detach_keyval_from_directory(struct csr1212_keyval *dir,

/* This function is used to free the memory taken by a keyval. If the given
* keyval is a directory type, then any keyvals contained in that directory
* will be destroyed as well if their respective refcnts are 0. By means of
* will be destroyed as well if noone holds a reference on them. By means of
* list manipulation, this routine will descend a directory structure in a
* non-recursive manner. */
static void csr1212_destroy_keyval(struct csr1212_keyval *kv)
void csr1212_release_keyval(struct csr1212_keyval *kv)
{
struct csr1212_keyval *k, *a;
struct csr1212_dentry dentry;
struct csr1212_dentry *head, *tail;

if (!atomic_dec_and_test(&kv->refcnt))
return;

dentry.kv = kv;
dentry.next = NULL;
dentry.prev = NULL;
Expand All @@ -503,9 +511,8 @@ static void csr1212_destroy_keyval(struct csr1212_keyval *kv)
k = head->kv;

while (k) {
k->refcnt--;

if (k->refcnt > 0)
/* must not dec_and_test kv->refcnt again */
if (k != kv && !atomic_dec_and_test(&k->refcnt))
break;

a = k->associate;
Expand Down Expand Up @@ -536,14 +543,6 @@ static void csr1212_destroy_keyval(struct csr1212_keyval *kv)
}
}

void csr1212_release_keyval(struct csr1212_keyval *kv)
{
if (kv->refcnt > 1)
kv->refcnt--;
else
csr1212_destroy_keyval(kv);
}

void csr1212_destroy_csr(struct csr1212_csr *csr)
{
struct csr1212_csr_rom_cache *c, *oc;
Expand Down Expand Up @@ -1126,6 +1125,7 @@ csr1212_parse_dir_entry(struct csr1212_keyval *dir, u32 ki, u32 kv_pos)
int ret = CSR1212_SUCCESS;
struct csr1212_keyval *k = NULL;
u32 offset;
bool keep_keyval = true;

switch (CSR1212_KV_KEY_TYPE(ki)) {
case CSR1212_KV_TYPE_IMMEDIATE:
Expand All @@ -1135,8 +1135,8 @@ csr1212_parse_dir_entry(struct csr1212_keyval *dir, u32 ki, u32 kv_pos)
ret = -ENOMEM;
goto out;
}

k->refcnt = 0; /* Don't keep local reference when parsing. */
/* Don't keep local reference when parsing. */
keep_keyval = false;
break;

case CSR1212_KV_TYPE_CSR_OFFSET:
Expand All @@ -1146,7 +1146,8 @@ csr1212_parse_dir_entry(struct csr1212_keyval *dir, u32 ki, u32 kv_pos)
ret = -ENOMEM;
goto out;
}
k->refcnt = 0; /* Don't keep local reference when parsing. */
/* Don't keep local reference when parsing. */
keep_keyval = false;
break;

default:
Expand Down Expand Up @@ -1174,16 +1175,18 @@ csr1212_parse_dir_entry(struct csr1212_keyval *dir, u32 ki, u32 kv_pos)
ret = -ENOMEM;
goto out;
}
k->refcnt = 0; /* Don't keep local reference when parsing. */
k->valid = 0; /* Contents not read yet so it's not valid. */
/* Don't keep local reference when parsing. */
keep_keyval = false;
/* Contents not read yet so it's not valid. */
k->valid = 0;
k->offset = offset;

k->prev = dir;
k->next = dir->next;
dir->next->prev = k;
dir->next = k;
}
ret = csr1212_attach_keyval_to_directory(dir, k);
ret = __csr1212_attach_keyval_to_directory(dir, k, keep_keyval);
out:
if (ret != CSR1212_SUCCESS && k != NULL)
free_keyval(k);
Expand Down
6 changes: 4 additions & 2 deletions drivers/ieee1394/csr1212.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@

#include <linux/types.h>
#include <linux/slab.h>
#include <asm/atomic.h>

#define CSR1212_MALLOC(size) kmalloc((size), GFP_KERNEL)
#define CSR1212_FREE(ptr) kfree(ptr)
Expand Down Expand Up @@ -149,7 +150,7 @@ struct csr1212_keyval {
struct csr1212_directory directory;
} value;
struct csr1212_keyval *associate;
int refcnt;
atomic_t refcnt;

/* used in generating and/or parsing CSR image */
struct csr1212_keyval *next, *prev; /* flat list of CSR elements */
Expand Down Expand Up @@ -350,7 +351,8 @@ csr1212_get_keyval(struct csr1212_csr *csr, struct csr1212_keyval *kv);
* need for code to retain a keyval that has been parsed. */
static inline void csr1212_keep_keyval(struct csr1212_keyval *kv)
{
kv->refcnt++;
atomic_inc(&kv->refcnt);
smp_mb__after_atomic_inc();
}


Expand Down
4 changes: 2 additions & 2 deletions drivers/ieee1394/nodemgr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1014,13 +1014,13 @@ static struct unit_directory *nodemgr_process_unit_directory
CSR1212_TEXTUAL_DESCRIPTOR_LEAF_LANGUAGE(kv) == 0) {
switch (last_key_id) {
case CSR1212_KV_ID_VENDOR:
ud->vendor_name_kv = kv;
csr1212_keep_keyval(kv);
ud->vendor_name_kv = kv;
break;

case CSR1212_KV_ID_MODEL:
ud->model_name_kv = kv;
csr1212_keep_keyval(kv);
ud->model_name_kv = kv;
break;

}
Expand Down

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