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rwlock_reader_lock: fix lock list jammed up

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This commit is contained in:
Tomoki Shirasawa
2016-03-03 22:47:48 +09:00
parent 8ebb3a4231
commit 26c0180374
2 changed files with 44 additions and 31 deletions
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62
arch/x86/kernel/include/arch-lock.h
View File

@ -13,7 +13,6 @@
#if defined(DEBUG_SPINLOCK) || defined(DEBUG_MCS_RWLOCK)
int __kprintf(const char *format, ...);
#endif
extern void panic(const char *);
typedef int ihk_spinlock_t;
@ -189,10 +188,8 @@ typedef struct mcs_rwlock_node {
char locked; // lock
#define MCS_RWLOCK_LOCKED 1
#define MCS_RWLOCK_UNLOCKED 0
char status;
#define MCS_RWLOCK_STAT_INACTIVE 0
#define MCS_RWLOCK_STAT_INPROGRESS 1
char dmy1; // unused
char dmy2; // unused
struct mcs_rwlock_node *next;
} __attribute__((aligned(64))) mcs_rwlock_node_t;
@ -211,7 +208,6 @@ mcs_rwlock_init(struct mcs_rwlock_lock *lock)
{
ihk_atomic_set(&lock->reader.count, 0);
lock->reader.type = MCS_RWLOCK_TYPE_COMMON_READER;
lock->reader.status = MCS_RWLOCK_STAT_INACTIVE;
lock->node = NULL;
}
@ -252,11 +248,12 @@ mcs_rwlock_unlock_readers(struct mcs_rwlock_lock *lock)
struct mcs_rwlock_node *p;
struct mcs_rwlock_node *f = NULL;
struct mcs_rwlock_node *n;
int breakf = 0;
ihk_atomic_inc(&lock->reader.count); // protect to unlock reader
for(p = &lock->reader; p->next; p = n){
n = p->next;
if(n->type == MCS_RWLOCK_TYPE_READER){
if(p->next->type == MCS_RWLOCK_TYPE_READER){
p->next = n->next;
if(lock->node == n){
struct mcs_rwlock_node *old;
@ -272,6 +269,9 @@ mcs_rwlock_unlock_readers(struct mcs_rwlock_lock *lock)
}
p->next = n->next;
}
else{
breakf = 1;
}
}
else if(p->next == NULL){
while (n->next == NULL) {
@ -286,6 +286,8 @@ mcs_rwlock_unlock_readers(struct mcs_rwlock_lock *lock)
else
f = n;
n = p;
if(breakf)
break;
}
if(n->next == NULL && lock->node != n){
while (n->next == NULL && lock->node != n) {
@ -294,7 +296,6 @@ mcs_rwlock_unlock_readers(struct mcs_rwlock_lock *lock)
}
}
lock->reader.status = MCS_RWLOCK_STAT_INACTIVE;
f->locked = MCS_RWLOCK_UNLOCKED;
}
@ -325,10 +326,6 @@ __mcs_rwlock_writer_unlock_noirq(struct mcs_rwlock_lock *lock, struct mcs_rwlock
}
if(node->next->type == MCS_RWLOCK_TYPE_READER){
if(lock->reader.status == MCS_RWLOCK_STAT_INPROGRESS){
panic("panic __mcs_rwlock_writer_unlock_noirq\n");
}
lock->reader.status = MCS_RWLOCK_STAT_INPROGRESS;
lock->reader.next = node->next;
mcs_rwlock_unlock_readers(lock);
}
@ -349,6 +346,24 @@ __kprintf("[%d] ret mcs_rwlock_reader_lock_noirq\n", ihk_mc_get_processor_id());
#else
#define mcs_rwlock_reader_lock_noirq __mcs_rwlock_reader_lock_noirq
#endif
static inline unsigned int
atomic_inc_ifnot0(ihk_atomic_t *v)
{
unsigned int *p = (unsigned int *)(&(v)->counter);
unsigned int old;
unsigned int new;
unsigned int val;
do{
if(!(old = *p))
break;
new = old + 1;
val = atomic_cmpxchg4(p, old, new);
}while(val != old);
return old;
}
static void
__mcs_rwlock_reader_lock_noirq(struct mcs_rwlock_lock *lock, struct mcs_rwlock_node *node)
{
@ -356,8 +371,6 @@ __mcs_rwlock_reader_lock_noirq(struct mcs_rwlock_lock *lock, struct mcs_rwlock_n
preempt_disable();
while(lock->reader.status != MCS_RWLOCK_STAT_INACTIVE)
cpu_pause();
node->type = MCS_RWLOCK_TYPE_READER;
node->next = NULL;
node->dmy1 = ihk_mc_get_processor_id();
@ -367,7 +380,7 @@ __mcs_rwlock_reader_lock_noirq(struct mcs_rwlock_lock *lock, struct mcs_rwlock_n
if (pred) {
if(pred == &lock->reader){
if(ihk_atomic_inc_return(&pred->count) != 1){
if(atomic_inc_ifnot0(&pred->count)){
struct mcs_rwlock_node *old;
old = (struct mcs_rwlock_node *)atomic_cmpxchg8(
@ -383,17 +396,12 @@ __mcs_rwlock_reader_lock_noirq(struct mcs_rwlock_lock *lock, struct mcs_rwlock_n
cpu_pause();
}
pred->next = node->next;
if(node->next->type == MCS_RWLOCK_TYPE_READER){
if(lock->reader.status == MCS_RWLOCK_STAT_INPROGRESS){
panic("panic __mcs_rwlock_reader_lock_noirq 1\n");
}
lock->reader.status = MCS_RWLOCK_STAT_INPROGRESS;
mcs_rwlock_unlock_readers(lock);
}
node->locked = MCS_RWLOCK_LOCKED;
lock->reader.next = node;
mcs_rwlock_unlock_readers(lock);
ihk_atomic_dec(&pred->count);
goto out;
}
ihk_atomic_dec(&pred->count);
}
node->locked = MCS_RWLOCK_LOCKED;
pred->next = node;
@ -402,10 +410,6 @@ panic("panic __mcs_rwlock_reader_lock_noirq 1\n");
}
}
else {
if(lock->reader.status == MCS_RWLOCK_STAT_INPROGRESS){
panic("panic __mcs_rwlock_reader_lock_noirq 2\n");
}
lock->reader.status = MCS_RWLOCK_STAT_INPROGRESS;
lock->reader.next = node;
mcs_rwlock_unlock_readers(lock);
}
@ -446,10 +450,6 @@ __mcs_rwlock_reader_unlock_noirq(struct mcs_rwlock_lock *lock, struct mcs_rwlock
}
if(lock->reader.next->type == MCS_RWLOCK_TYPE_READER){
if(lock->reader.status == MCS_RWLOCK_STAT_INPROGRESS){
panic("panic __mcs_rwlock_reader_unlock_noirq\n");
}
lock->reader.status = MCS_RWLOCK_STAT_INPROGRESS;
mcs_rwlock_unlock_readers(lock);
}
else{

13
arch/x86/kernel/include/ihk/atomic.h
View File

@ -202,4 +202,17 @@ static inline unsigned long atomic_cmpxchg8(unsigned long *addr,
return oldval;
}
static inline unsigned long atomic_cmpxchg4(unsigned int *addr,
unsigned int oldval,
unsigned int newval)
{
asm volatile("lock; cmpxchgl %2, %1\n"
: "=a" (oldval), "+m" (*addr)
: "r" (newval), "0" (oldval)
: "memory"
);
return oldval;
}
#endif