* Distributed under GPLv2
*/
+#include <stdlib.h>
+
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
: "+m" (*v));
}
+#define xchg(ptr, v) \
+ ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), sizeof(*(ptr))))
+
+struct __xchg_dummy {
+ unsigned long a[100];
+};
+#define __xg(x) ((struct __xchg_dummy *)(x))
+
+/*
+ * Note: no "lock" prefix even on SMP: xchg always implies lock anyway
+ * Note 2: xchg has side effect, so that attribute volatile is necessary,
+ * but generally the primitive is invalid, *ptr is output argument. --ANK
+ */
+static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
+ int size)
+{
+ switch (size) {
+ case 1:
+ asm volatile("xchgb %b0,%1"
+ : "=q" (x)
+ : "m" (*__xg(ptr)), "0" (x)
+ : "memory");
+ break;
+ case 2:
+ asm volatile("xchgw %w0,%1"
+ : "=r" (x)
+ : "m" (*__xg(ptr)), "0" (x)
+ : "memory");
+ break;
+ case 4:
+ asm volatile("xchgl %0,%1"
+ : "=r" (x)
+ : "m" (*__xg(ptr)), "0" (x)
+ : "memory");
+ break;
+ }
+ return x;
+}
+
/* Nop everywhere except on alpha. */
#define smp_read_barrier_depends()
#define SIGURCU SIGUSR1
-/* Global quiescent period parity */
-extern int urcu_qparity;
+#ifdef DEBUG_YIELD
+#include <sched.h>
+
+#define YIELD_READ (1 << 0)
+#define YIELD_WRITE (1 << 1)
+
+extern unsigned int yield_active;
+extern unsigned int __thread rand_yield;
+
+static inline void debug_yield_read(void)
+{
+ if (yield_active & YIELD_READ)
+ if (rand_r(&rand_yield) & 0x1)
+ sched_yield();
+}
+
+static inline void debug_yield_write(void)
+{
+ if (yield_active & YIELD_WRITE)
+ if (rand_r(&rand_yield) & 0x1)
+ sched_yield();
+}
+
+static inline void debug_yield_init(void)
+{
+ rand_yield = time(NULL) ^ pthread_self();
+}
+#else
+static inline void debug_yield_read(void)
+{
+}
-extern int __thread urcu_active_readers[2];
+static inline void debug_yield_write(void)
+{
+}
-static inline int get_urcu_qparity(void)
+static inline void debug_yield_init(void)
{
- return urcu_qparity;
+
}
+#endif
/*
- * returns urcu_parity.
+ * Limiting the nesting level to 256 to keep instructions small in the read
+ * fast-path.
*/
-static inline int rcu_read_lock(void)
+#define RCU_GP_COUNT (1U << 0)
+#define RCU_GP_CTR_BIT (1U << 8)
+#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
+
+/* Global quiescent period counter with low-order bits unused. */
+extern int urcu_gp_ctr;
+
+extern int __thread urcu_active_readers;
+
+static inline int rcu_old_gp_ongoing(int *value)
{
- int urcu_parity = get_urcu_qparity();
- urcu_active_readers[urcu_parity]++;
+ int v;
+
+ if (value == NULL)
+ return 0;
+ debug_yield_write();
+ v = ACCESS_ONCE(*value);
+ debug_yield_write();
+ return (v & RCU_GP_CTR_NEST_MASK) &&
+ ((v ^ ACCESS_ONCE(urcu_gp_ctr)) & RCU_GP_CTR_BIT);
+}
+
+static inline void rcu_read_lock(void)
+{
+ int tmp;
+
+ debug_yield_read();
+ tmp = urcu_active_readers;
+ debug_yield_read();
+ if (!(tmp & RCU_GP_CTR_NEST_MASK))
+ urcu_active_readers = urcu_gp_ctr + RCU_GP_COUNT;
+ else
+ urcu_active_readers = tmp + RCU_GP_COUNT;
+ debug_yield_read();
/*
* Increment active readers count before accessing the pointer.
* See force_mb_all_threads().
*/
barrier();
- return urcu_parity;
+ debug_yield_read();
}
-static inline void rcu_read_unlock(int urcu_parity)
+static inline void rcu_read_unlock(void)
{
+ debug_yield_read();
barrier();
+ debug_yield_read();
/*
* Finish using rcu before decrementing the pointer.
* See force_mb_all_threads().
*/
- urcu_active_readers[urcu_parity]--;
+ urcu_active_readers -= RCU_GP_COUNT;
+ debug_yield_read();
}
-extern void rcu_write_lock(void);
-extern void rcu_write_unlock(void);
+/**
+ * rcu_assign_pointer - assign (publicize) a pointer to a newly
+ * initialized structure that will be dereferenced by RCU read-side
+ * critical sections. Returns the value assigned.
+ *
+ * Inserts memory barriers on architectures that require them
+ * (pretty much all of them other than x86), and also prevents
+ * the compiler from reordering the code that initializes the
+ * structure after the pointer assignment. More importantly, this
+ * call documents which pointers will be dereferenced by RCU read-side
+ * code.
+ */
+
+#define rcu_assign_pointer(p, v) \
+ ({ \
+ if (!__builtin_constant_p(v) || \
+ ((v) != NULL)) \
+ wmb(); \
+ (p) = (v); \
+ })
+
+#define rcu_xchg_pointer(p, v) \
+ ({ \
+ if (!__builtin_constant_p(v) || \
+ ((v) != NULL)) \
+ wmb(); \
+ xchg(p, v); \
+ })
-extern void *_urcu_publish_content(void **ptr, void *new);
+extern void synchronize_rcu(void);
/*
- * gcc does not like automatic &struct ... * -> void **.
- * Remove the warning. (hopefully this is ok)
+ * Exchanges the pointer and waits for quiescent state.
+ * The pointer returned can be freed.
*/
-#define urcu_publish_content(ptr, new) _urcu_publish_content((void **)ptr, new)
+#define urcu_publish_content(p, v) \
+ ({ \
+ void *oldptr; \
+ debug_yield_write(); \
+ oldptr = rcu_xchg_pointer(p, v); \
+ synchronize_rcu(); \
+ oldptr; \
+ })
/*
* Reader thread registration.