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qemu-lock.h: Remove non-pthreads spinlock implementations

Since configure guarantees us that we have pthreads on all hosts
except mingw (which doesn't support a USER_ONLY config), we can
and should use the pthread_mutex based implementation of spin_lock()
and spin_unlock() in all USER_ONLY cases. This means that all the
inline-native-assembly code supporting the "USER_ONLY but not USE_NPTL"
case can go away.

The not-USER_ONLY case remains as empty implementations; there is
no change in behaviour here.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
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1 parent 322fd48 commit 02615337ef295443daa03233e492194e289a807e @pm215 pm215 committed with aurel32 Jan 31, 2011
Showing with 11 additions and 199 deletions.
  1. +11 −199 qemu-lock.h
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@@ -15,15 +15,11 @@
* License along with this library; if not, see <http://www.gnu.org/licenses/>
*/
-/* Locking primitives. Most of this code should be redundant -
- system emulation doesn't need/use locking, NPTL userspace uses
- pthread mutexes, and non-NPTL userspace isn't threadsafe anyway.
- In either case a spinlock is probably the wrong kind of lock.
- Spinlocks are only good if you know annother CPU has the lock and is
- likely to release it soon. In environments where you have more threads
- than physical CPUs (the extreme case being a single CPU host) a spinlock
- simply wastes CPU until the OS decides to preempt it. */
-#if defined(CONFIG_USE_NPTL)
+/* configure guarantees us that we have pthreads on any host except
+ * mingw32, which doesn't support any of the user-only targets.
+ * So we can simply assume we have pthread mutexes here.
+ */
+#if defined(CONFIG_USER_ONLY)
#include <pthread.h>
#define spin_lock pthread_mutex_lock
@@ -33,205 +29,21 @@
#else
-#if defined(__hppa__)
-
-typedef int spinlock_t[4];
-
-#define SPIN_LOCK_UNLOCKED { 1, 1, 1, 1 }
-
-static inline void resetlock (spinlock_t *p)
-{
- (*p)[0] = (*p)[1] = (*p)[2] = (*p)[3] = 1;
-}
-
-#else
-
+/* Empty implementations, on the theory that system mode emulation
+ * is single-threaded. This means that these functions should only
+ * be used from code run in the TCG cpu thread, and cannot protect
+ * data structures which might also be accessed from the IO thread
+ * or from signal handlers.
+ */
typedef int spinlock_t;
-
#define SPIN_LOCK_UNLOCKED 0
-static inline void resetlock (spinlock_t *p)
-{
- *p = SPIN_LOCK_UNLOCKED;
-}
-
-#endif
-
-#if defined(_ARCH_PPC)
-static inline int testandset (int *p)
-{
- int ret;
- __asm__ __volatile__ (
- " lwarx %0,0,%1\n"
- " xor. %0,%3,%0\n"
- " bne $+12\n"
- " stwcx. %2,0,%1\n"
- " bne- $-16\n"
- : "=&r" (ret)
- : "r" (p), "r" (1), "r" (0)
- : "cr0", "memory");
- return ret;
-}
-#elif defined(__i386__)
-static inline int testandset (int *p)
-{
- long int readval = 0;
-
- __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
- : "+m" (*p), "+a" (readval)
- : "r" (1)
- : "cc");
- return readval;
-}
-#elif defined(__x86_64__)
-static inline int testandset (int *p)
-{
- long int readval = 0;
-
- __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
- : "+m" (*p), "+a" (readval)
- : "r" (1)
- : "cc");
- return readval;
-}
-#elif defined(__s390__)
-static inline int testandset (int *p)
-{
- int ret;
-
- __asm__ __volatile__ ("0: cs %0,%1,0(%2)\n"
- " jl 0b"
- : "=&d" (ret)
- : "r" (1), "a" (p), "0" (*p)
- : "cc", "memory" );
- return ret;
-}
-#elif defined(__alpha__)
-static inline int testandset (int *p)
-{
- int ret;
- unsigned long one;
-
- __asm__ __volatile__ ("0: mov 1,%2\n"
- " ldl_l %0,%1\n"
- " stl_c %2,%1\n"
- " beq %2,1f\n"
- ".subsection 2\n"
- "1: br 0b\n"
- ".previous"
- : "=r" (ret), "=m" (*p), "=r" (one)
- : "m" (*p));
- return ret;
-}
-#elif defined(__sparc__)
-static inline int testandset (int *p)
-{
- int ret;
-
- __asm__ __volatile__("ldstub [%1], %0"
- : "=r" (ret)
- : "r" (p)
- : "memory");
-
- return (ret ? 1 : 0);
-}
-#elif defined(__arm__)
-static inline int testandset (int *spinlock)
-{
- register unsigned int ret;
- __asm__ __volatile__("swp %0, %1, [%2]"
- : "=r"(ret)
- : "0"(1), "r"(spinlock));
-
- return ret;
-}
-#elif defined(__mc68000)
-static inline int testandset (int *p)
-{
- char ret;
- __asm__ __volatile__("tas %1; sne %0"
- : "=r" (ret)
- : "m" (p)
- : "cc","memory");
- return ret;
-}
-#elif defined(__hppa__)
-
-/* Because malloc only guarantees 8-byte alignment for malloc'd data,
- and GCC only guarantees 8-byte alignment for stack locals, we can't
- be assured of 16-byte alignment for atomic lock data even if we
- specify "__attribute ((aligned(16)))" in the type declaration. So,
- we use a struct containing an array of four ints for the atomic lock
- type and dynamically select the 16-byte aligned int from the array
- for the semaphore. */
-#define __PA_LDCW_ALIGNMENT 16
-static inline void *ldcw_align (void *p) {
- unsigned long a = (unsigned long)p;
- a = (a + __PA_LDCW_ALIGNMENT - 1) & ~(__PA_LDCW_ALIGNMENT - 1);
- return (void *)a;
-}
-
-static inline int testandset (spinlock_t *p)
-{
- unsigned int ret;
- p = ldcw_align(p);
- __asm__ __volatile__("ldcw 0(%1),%0"
- : "=r" (ret)
- : "r" (p)
- : "memory" );
- return !ret;
-}
-
-#elif defined(__ia64)
-
-#include <ia64intrin.h>
-
-static inline int testandset (int *p)
-{
- return __sync_lock_test_and_set (p, 1);
-}
-#elif defined(__mips__)
-static inline int testandset (int *p)
-{
- int ret;
-
- __asm__ __volatile__ (
- " .set push \n"
- " .set noat \n"
- " .set mips2 \n"
- "1: li $1, 1 \n"
- " ll %0, %1 \n"
- " sc $1, %1 \n"
- " beqz $1, 1b \n"
- " .set pop "
- : "=r" (ret), "+R" (*p)
- :
- : "memory");
-
- return ret;
-}
-#else
-#error unimplemented CPU support
-#endif
-
-#if defined(CONFIG_USER_ONLY)
-static inline void spin_lock(spinlock_t *lock)
-{
- while (testandset(lock));
-}
-
-static inline void spin_unlock(spinlock_t *lock)
-{
- resetlock(lock);
-}
-#else
static inline void spin_lock(spinlock_t *lock)
{
}
static inline void spin_unlock(spinlock_t *lock)
{
}
-#endif
#endif

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