SMP memory barriers are reduced to compiler barriers on uniprocessor compiled
systems because it is assumed that a CPU will appear to be self-consistent,
and will order overlapping accesses correctly with respect to itself.
+However, see the subsection on "Virtual Machine Guests" below.
[!] Note that SMP memory barriers _must_ be used to control the ordering of
references to shared memory on SMP systems, though the use of locking instead
is sufficient.
Mandatory barriers should not be used to control SMP effects, since mandatory
-barriers unnecessarily impose overhead on UP systems. They may, however, be
-used to control MMIO effects on accesses through relaxed memory I/O windows.
-These are required even on non-SMP systems as they affect the order in which
-memory operations appear to a device by prohibiting both the compiler and the
-CPU from reordering them.
+barriers impose unnecessary overhead on both SMP and UP systems. They may,
+however, be used to control MMIO effects on accesses through relaxed memory I/O
+windows. These barriers are required even on non-SMP systems as they affect
+the order in which memory operations appear to a device by prohibiting both the
+compiler and the CPU from reordering them.
There are some more advanced barrier functions:
See the subsection on "Cache Coherency" above.
+VIRTUAL MACHINE GUESTS
+-------------------
+
+Guests running within virtual machines might be affected by SMP effects even if
+the guest itself is compiled without SMP support. This is an artifact of
+interfacing with an SMP host while running an UP kernel. Using mandatory
+barriers for this use-case would be possible but is often suboptimal.
+
+To handle this case optimally, low-level virt_mb() etc macros are available.
+These have the same effect as smp_mb() etc when SMP is enabled, but generate
+identical code for SMP and non-SMP systems. For example, virtual machine guests
+should use virt_mb() rather than smp_mb() when synchronizing against a
+(possibly SMP) host.
+
+These are equivalent to smp_mb() etc counterparts in all other respects,
+in particular, they do not control MMIO effects: to control
+MMIO effects, use mandatory barriers.
============
EXAMPLE USES
#define dma_wmb() barrier()
#endif
-#ifndef CONFIG_SMP
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
-#else
-#define smp_mb() dmb(ish)
-#define smp_rmb() smp_mb()
-#define smp_wmb() dmb(ishst)
-#endif
-
-#define smp_store_release(p, v) \
-do { \
- compiletime_assert_atomic_type(*p); \
- smp_mb(); \
- WRITE_ONCE(*p, v); \
-} while (0)
-
-#define smp_load_acquire(p) \
-({ \
- typeof(*p) ___p1 = READ_ONCE(*p); \
- compiletime_assert_atomic_type(*p); \
- smp_mb(); \
- ___p1; \
-})
-
-#define read_barrier_depends() do { } while(0)
-#define smp_read_barrier_depends() do { } while(0)
-
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
+#define __smp_mb() dmb(ish)
+#define __smp_rmb() __smp_mb()
+#define __smp_wmb() dmb(ishst)
-#define smp_mb__before_atomic() smp_mb()
-#define smp_mb__after_atomic() smp_mb()
+#include <asm-generic/barrier.h>
#endif /* !__ASSEMBLY__ */
#endif /* __ASM_BARRIER_H */
#define dma_rmb() dmb(oshld)
#define dma_wmb() dmb(oshst)
-#define smp_mb() dmb(ish)
-#define smp_rmb() dmb(ishld)
-#define smp_wmb() dmb(ishst)
+#define __smp_mb() dmb(ish)
+#define __smp_rmb() dmb(ishld)
+#define __smp_wmb() dmb(ishst)
-#define smp_store_release(p, v) \
+#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
switch (sizeof(*p)) { \
} \
} while (0)
-#define smp_load_acquire(p) \
+#define __smp_load_acquire(p) \
({ \
union { typeof(*p) __val; char __c[1]; } __u; \
compiletime_assert_atomic_type(*p); \
__u.__val; \
})
-#define read_barrier_depends() do { } while(0)
-#define smp_read_barrier_depends() do { } while(0)
-
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
-#define nop() asm volatile("nop");
-
-#define smp_mb__before_atomic() smp_mb()
-#define smp_mb__after_atomic() smp_mb()
+#include <asm-generic/barrier.h>
#endif /* __ASSEMBLY__ */
#endif /* !CONFIG_SMP */
-#define smp_mb__before_atomic() barrier()
-#define smp_mb__after_atomic() barrier()
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
#include <asm-generic/barrier.h>
#define dma_rmb() mb()
#define dma_wmb() mb()
-#ifdef CONFIG_SMP
-# define smp_mb() mb()
-#else
-# define smp_mb() barrier()
-#endif
+# define __smp_mb() mb()
-#define smp_rmb() smp_mb()
-#define smp_wmb() smp_mb()
-
-#define read_barrier_depends() do { } while (0)
-#define smp_read_barrier_depends() do { } while (0)
-
-#define smp_mb__before_atomic() barrier()
-#define smp_mb__after_atomic() barrier()
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
/*
* IA64 GCC turns volatile stores into st.rel and volatile loads into ld.acq no
* need for asm trickery!
*/
-#define smp_store_release(p, v) \
+#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
barrier(); \
WRITE_ONCE(*p, v); \
} while (0)
-#define smp_load_acquire(p) \
+#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
___p1; \
})
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
-
/*
* The group barrier in front of the rsm & ssm are necessary to ensure
* that none of the previous instructions in the same group are
* affected by the rsm/ssm.
*/
+#include <asm-generic/barrier.h>
+
#endif /* _ASM_IA64_BARRIER_H */
}
static void
-nop (struct irq_data *data)
+iosapic_nop (struct irq_data *data)
{
/* do nothing... */
}
#define iosapic_shutdown_level_irq mask_irq
#define iosapic_enable_level_irq unmask_irq
#define iosapic_disable_level_irq mask_irq
-#define iosapic_ack_level_irq nop
+#define iosapic_ack_level_irq iosapic_nop
static struct irq_chip irq_type_iosapic_level = {
.name = "IO-SAPIC-level",
}
#define iosapic_enable_edge_irq unmask_irq
-#define iosapic_disable_edge_irq nop
+#define iosapic_disable_edge_irq iosapic_nop
static struct irq_chip irq_type_iosapic_edge = {
.name = "IO-SAPIC-edge",
#define rmb() barrier()
#define wmb() mb()
-#define dma_rmb() rmb()
-#define dma_wmb() wmb()
-
-#ifndef CONFIG_SMP
-#define fence() do { } while (0)
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
-#else
-
#ifdef CONFIG_METAG_SMP_WRITE_REORDERING
/*
* Write to the atomic memory unlock system event register (command 0). This is
* incoherence). It is therefore ineffective if used after and on the same
* thread as a write.
*/
-static inline void fence(void)
+static inline void metag_fence(void)
{
volatile int *flushptr = (volatile int *) LINSYSEVENT_WR_ATOMIC_UNLOCK;
barrier();
*flushptr = 0;
barrier();
}
-#define smp_mb() fence()
-#define smp_rmb() fence()
-#define smp_wmb() barrier()
+#define __smp_mb() metag_fence()
+#define __smp_rmb() metag_fence()
+#define __smp_wmb() barrier()
#else
-#define fence() do { } while (0)
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
-#endif
+#define metag_fence() do { } while (0)
+#define __smp_mb() barrier()
+#define __smp_rmb() barrier()
+#define __smp_wmb() barrier()
#endif
-#define read_barrier_depends() do { } while (0)
-#define smp_read_barrier_depends() do { } while (0)
-
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
-
-#define smp_store_release(p, v) \
-do { \
- compiletime_assert_atomic_type(*p); \
- smp_mb(); \
- WRITE_ONCE(*p, v); \
-} while (0)
+#ifdef CONFIG_SMP
+#define fence() metag_fence()
+#else
+#define fence() do { } while (0)
+#endif
-#define smp_load_acquire(p) \
-({ \
- typeof(*p) ___p1 = READ_ONCE(*p); \
- compiletime_assert_atomic_type(*p); \
- smp_mb(); \
- ___p1; \
-})
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
-#define smp_mb__before_atomic() barrier()
-#define smp_mb__after_atomic() barrier()
+#include <asm-generic/barrier.h>
#endif /* _ASM_METAG_BARRIER_H */
#include <asm/addrspace.h>
-#define read_barrier_depends() do { } while(0)
-#define smp_read_barrier_depends() do { } while(0)
-
#ifdef CONFIG_CPU_HAS_SYNC
#define __sync() \
__asm__ __volatile__( \
#define wmb() fast_wmb()
#define rmb() fast_rmb()
-#define dma_wmb() fast_wmb()
-#define dma_rmb() fast_rmb()
-#if defined(CONFIG_WEAK_ORDERING) && defined(CONFIG_SMP)
+#if defined(CONFIG_WEAK_ORDERING)
# ifdef CONFIG_CPU_CAVIUM_OCTEON
-# define smp_mb() __sync()
-# define smp_rmb() barrier()
-# define smp_wmb() __syncw()
+# define __smp_mb() __sync()
+# define __smp_rmb() barrier()
+# define __smp_wmb() __syncw()
# else
-# define smp_mb() __asm__ __volatile__("sync" : : :"memory")
-# define smp_rmb() __asm__ __volatile__("sync" : : :"memory")
-# define smp_wmb() __asm__ __volatile__("sync" : : :"memory")
+# define __smp_mb() __asm__ __volatile__("sync" : : :"memory")
+# define __smp_rmb() __asm__ __volatile__("sync" : : :"memory")
+# define __smp_wmb() __asm__ __volatile__("sync" : : :"memory")
# endif
#else
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
+#define __smp_mb() barrier()
+#define __smp_rmb() barrier()
+#define __smp_wmb() barrier()
#endif
#if defined(CONFIG_WEAK_REORDERING_BEYOND_LLSC) && defined(CONFIG_SMP)
#define __WEAK_LLSC_MB " \n"
#endif
-#define smp_store_mb(var, value) \
- do { WRITE_ONCE(var, value); smp_mb(); } while (0)
-
#define smp_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory")
#ifdef CONFIG_CPU_CAVIUM_OCTEON
#define smp_mb__before_llsc() smp_wmb()
+#define __smp_mb__before_llsc() __smp_wmb()
/* Cause previous writes to become visible on all CPUs as soon as possible */
#define nudge_writes() __asm__ __volatile__(".set push\n\t" \
".set arch=octeon\n\t" \
".set pop" : : : "memory")
#else
#define smp_mb__before_llsc() smp_llsc_mb()
+#define __smp_mb__before_llsc() smp_llsc_mb()
#define nudge_writes() mb()
#endif
-#define smp_store_release(p, v) \
-do { \
- compiletime_assert_atomic_type(*p); \
- smp_mb(); \
- WRITE_ONCE(*p, v); \
-} while (0)
-
-#define smp_load_acquire(p) \
-({ \
- typeof(*p) ___p1 = READ_ONCE(*p); \
- compiletime_assert_atomic_type(*p); \
- smp_mb(); \
- ___p1; \
-})
-
-#define smp_mb__before_atomic() smp_mb__before_llsc()
-#define smp_mb__after_atomic() smp_llsc_mb()
+#define __smp_mb__before_atomic() __smp_mb__before_llsc()
+#define __smp_mb__after_atomic() smp_llsc_mb()
+
+#include <asm-generic/barrier.h>
#endif /* __ASM_BARRIER_H */
#define rmb() __asm__ __volatile__ ("sync" : : : "memory")
#define wmb() __asm__ __volatile__ ("sync" : : : "memory")
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
-
#ifdef __SUBARCH_HAS_LWSYNC
# define SMPWMB LWSYNC
#else
#define dma_rmb() __lwsync()
#define dma_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
-#ifdef CONFIG_SMP
-#define smp_lwsync() __lwsync()
-
-#define smp_mb() mb()
-#define smp_rmb() __lwsync()
-#define smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
-#else
-#define smp_lwsync() barrier()
+#define __smp_lwsync() __lwsync()
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
-#endif /* CONFIG_SMP */
-
-#define read_barrier_depends() do { } while (0)
-#define smp_read_barrier_depends() do { } while (0)
+#define __smp_mb() mb()
+#define __smp_rmb() __lwsync()
+#define __smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
/*
* This is a barrier which prevents following instructions from being
#define data_barrier(x) \
asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory");
-#define smp_store_release(p, v) \
+#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
- smp_lwsync(); \
+ __smp_lwsync(); \
WRITE_ONCE(*p, v); \
} while (0)
-#define smp_load_acquire(p) \
+#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
- smp_lwsync(); \
+ __smp_lwsync(); \
___p1; \
})
-#define smp_mb__before_atomic() smp_mb()
-#define smp_mb__after_atomic() smp_mb()
#define smp_mb__before_spinlock() smp_mb()
+#include <asm-generic/barrier.h>
+
#endif /* _ASM_POWERPC_BARRIER_H */
#define wmb() barrier()
#define dma_rmb() mb()
#define dma_wmb() mb()
-#define smp_mb() mb()
-#define smp_rmb() rmb()
-#define smp_wmb() wmb()
+#define __smp_mb() mb()
+#define __smp_rmb() rmb()
+#define __smp_wmb() wmb()
-#define read_barrier_depends() do { } while (0)
-#define smp_read_barrier_depends() do { } while (0)
-
-#define smp_mb__before_atomic() smp_mb()
-#define smp_mb__after_atomic() smp_mb()
-
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
-
-#define smp_store_release(p, v) \
+#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
barrier(); \
WRITE_ONCE(*p, v); \
} while (0)
-#define smp_load_acquire(p) \
+#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
___p1; \
})
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
+
+#include <asm-generic/barrier.h>
+
#endif /* __ASM_BARRIER_H */
#define ctrl_barrier() __asm__ __volatile__ ("nop;nop;nop;nop;nop;nop;nop;nop")
#endif
-#define smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
+#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
+#define smp_store_mb(var, value) __smp_store_mb(var, value)
#include <asm-generic/barrier.h>
return retval;
}
+static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
+{
+ unsigned long retval;
+
+ __asm__ __volatile__ (
+ " .align 2 \n\t"
+ " mova 1f, r0 \n\t" /* r0 = end point */
+ " mov r15, r1 \n\t" /* r1 = saved sp */
+ " mov #-6, r15 \n\t" /* LOGIN */
+ " mov.w @%1, %0 \n\t" /* load old value */
+ " extu.w %0, %0 \n\t" /* extend as unsigned */
+ " mov.w %2, @%1 \n\t" /* store new value */
+ "1: mov r1, r15 \n\t" /* LOGOUT */
+ : "=&r" (retval),
+ "+r" (m),
+ "+r" (val) /* inhibit r15 overloading */
+ :
+ : "memory" , "r0", "r1");
+
+ return retval;
+}
+
static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
{
unsigned long retval;
return retval;
}
+static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
+{
+ unsigned long flags, retval;
+
+ local_irq_save(flags);
+ retval = *m;
+ *m = val;
+ local_irq_restore(flags);
+ return retval;
+}
+
static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
{
unsigned long flags, retval;
return retval;
}
-static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
-{
- unsigned long retval;
- unsigned long tmp;
-
- __asm__ __volatile__ (
- "1: \n\t"
- "movli.l @%2, %0 ! xchg_u8 \n\t"
- "mov %0, %1 \n\t"
- "mov %3, %0 \n\t"
- "movco.l %0, @%2 \n\t"
- "bf 1b \n\t"
- "synco \n\t"
- : "=&z"(tmp), "=&r" (retval)
- : "r" (m), "r" (val & 0xff)
- : "t", "memory"
- );
-
- return retval;
-}
-
static inline unsigned long
-__cmpxchg_u32(volatile int *m, unsigned long old, unsigned long new)
+__cmpxchg_u32(volatile u32 *m, unsigned long old, unsigned long new)
{
unsigned long retval;
unsigned long tmp;
return retval;
}
+#include <asm/cmpxchg-xchg.h>
+
#endif /* __ASM_SH_CMPXCHG_LLSC_H */
--- /dev/null
+#ifndef __ASM_SH_CMPXCHG_XCHG_H
+#define __ASM_SH_CMPXCHG_XCHG_H
+
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See the
+ * file "COPYING" in the main directory of this archive for more details.
+ */
+#include <linux/bitops.h>
+#include <asm/byteorder.h>
+
+/*
+ * Portable implementations of 1 and 2 byte xchg using a 4 byte cmpxchg.
+ * Note: this header isn't self-contained: before including it, __cmpxchg_u32
+ * must be defined first.
+ */
+static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size)
+{
+ int off = (unsigned long)ptr % sizeof(u32);
+ volatile u32 *p = ptr - off;
+#ifdef __BIG_ENDIAN
+ int bitoff = (sizeof(u32) - 1 - off) * BITS_PER_BYTE;
+#else
+ int bitoff = off * BITS_PER_BYTE;
+#endif
+ u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
+ u32 oldv, newv;
+ u32 ret;
+
+ do {
+ oldv = READ_ONCE(*p);
+ ret = (oldv & bitmask) >> bitoff;
+ newv = (oldv & ~bitmask) | (x << bitoff);
+ } while (__cmpxchg_u32(p, oldv, newv) != oldv);
+
+ return ret;
+}
+
+static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
+{
+ return __xchg_cmpxchg(m, val, sizeof *m);
+}
+
+static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
+{
+ return __xchg_cmpxchg(m, val, sizeof *m);
+}
+
+#endif /* __ASM_SH_CMPXCHG_XCHG_H */
case 4: \
__xchg__res = xchg_u32(__xchg_ptr, x); \
break; \
+ case 2: \
+ __xchg__res = xchg_u16(__xchg_ptr, x); \
+ break; \
case 1: \
__xchg__res = xchg_u8(__xchg_ptr, x); \
break; \
#ifndef __SPARC_BARRIER_H
#define __SPARC_BARRIER_H
-#include <asm/processor.h> /* for nop() */
#include <asm-generic/barrier.h>
#endif /* !(__SPARC_BARRIER_H) */
#define rmb() __asm__ __volatile__("":::"memory")
#define wmb() __asm__ __volatile__("":::"memory")
-#define dma_rmb() rmb()
-#define dma_wmb() wmb()
-
-#define smp_store_mb(__var, __value) \
- do { WRITE_ONCE(__var, __value); membar_safe("#StoreLoad"); } while(0)
-
-#ifdef CONFIG_SMP
-#define smp_mb() mb()
-#define smp_rmb() rmb()
-#define smp_wmb() wmb()
-#else
-#define smp_mb() __asm__ __volatile__("":::"memory")
-#define smp_rmb() __asm__ __volatile__("":::"memory")
-#define smp_wmb() __asm__ __volatile__("":::"memory")
-#endif
-
-#define read_barrier_depends() do { } while (0)
-#define smp_read_barrier_depends() do { } while (0)
-
-#define smp_store_release(p, v) \
+#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
barrier(); \
WRITE_ONCE(*p, v); \
} while (0)
-#define smp_load_acquire(p) \
+#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
___p1; \
})
-#define smp_mb__before_atomic() barrier()
-#define smp_mb__after_atomic() barrier()
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
+
+#include <asm-generic/barrier.h>
#endif /* !(__SPARC64_BARRIER_H) */
#else
#include <asm/processor_32.h>
#endif
-
-#define nop() __asm__ __volatile__ ("nop")
-
#endif
* But after the word is updated, the routine issues an "mf" before returning,
* and since it's a function call, we don't even need a compiler barrier.
*/
-#define smp_mb__before_atomic() smp_mb()
-#define smp_mb__after_atomic() do { } while (0)
+#define __smp_mb__before_atomic() __smp_mb()
+#define __smp_mb__after_atomic() do { } while (0)
+#define smp_mb__after_atomic() __smp_mb__after_atomic()
#else /* 64 bit */
-#define smp_mb__before_atomic() smp_mb()
-#define smp_mb__after_atomic() smp_mb()
+#define __smp_mb__before_atomic() __smp_mb()
+#define __smp_mb__after_atomic() __smp_mb()
#endif
#include <asm-generic/barrier.h>
#endif
#define dma_wmb() barrier()
-#ifdef CONFIG_SMP
-#define smp_mb() mb()
-#define smp_rmb() dma_rmb()
-#define smp_wmb() barrier()
-#define smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
-#else /* !SMP */
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0)
-#endif /* SMP */
-
-#define read_barrier_depends() do { } while (0)
-#define smp_read_barrier_depends() do { } while (0)
+#define __smp_mb() mb()
+#define __smp_rmb() dma_rmb()
+#define __smp_wmb() barrier()
+#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
#if defined(CONFIG_X86_PPRO_FENCE)
* model and we should fall back to full barriers.
*/
-#define smp_store_release(p, v) \
+#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
- smp_mb(); \
+ __smp_mb(); \
WRITE_ONCE(*p, v); \
} while (0)
-#define smp_load_acquire(p) \
+#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
- smp_mb(); \
+ __smp_mb(); \
___p1; \
})
#else /* regular x86 TSO memory ordering */
-#define smp_store_release(p, v) \
+#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
barrier(); \
WRITE_ONCE(*p, v); \
} while (0)
-#define smp_load_acquire(p) \
+#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
#endif
/* Atomic operations are already serializing on x86 */
-#define smp_mb__before_atomic() barrier()
-#define smp_mb__after_atomic() barrier()
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
+
+#include <asm-generic/barrier.h>
#endif /* _ASM_X86_BARRIER_H */
#endif /* CONFIG_X86_PPRO_FENCE */
#define dma_wmb() barrier()
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
-
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0)
-
-#define read_barrier_depends() do { } while (0)
-#define smp_read_barrier_depends() do { } while (0)
+#include <asm-generic/barrier.h>
#endif
#define rmb() barrier()
#define wmb() mb()
-#define smp_mb__before_atomic() barrier()
-#define smp_mb__after_atomic() barrier()
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
#include <asm-generic/barrier.h>
static vq_callback_t *callbacks[] = {
virtio_gpu_ctrl_ack, virtio_gpu_cursor_ack
};
- static const char *names[] = { "control", "cursor" };
+ static const char * const names[] = { "control", "cursor" };
struct virtio_gpu_device *vgdev;
/* this will expand later */
static int mic_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[])
+ const char * const names[])
{
struct mic_vdev *mvdev = to_micvdev(vdev);
struct mic_device_ctrl __iomem *dc = mvdev->dc;
static int rproc_virtio_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[])
+ const char * const names[])
{
struct rproc *rproc = vdev_to_rproc(vdev);
int i, ret;
static int rpmsg_probe(struct virtio_device *vdev)
{
vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
- const char *names[] = { "input", "output" };
+ static const char * const names[] = { "input", "output" };
struct virtqueue *vqs[2];
struct virtproc_info *vrp;
void *bufs_va;
static int kvm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[])
+ const char * const names[])
{
struct kvm_device *kdev = to_kvmdev(vdev);
int i;
static int virtio_ccw_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[])
+ const char * const names[])
{
struct virtio_ccw_device *vcdev = to_vc_device(vdev);
unsigned long *indicatorp = NULL;
*/
if (vb->num_pfns != 0)
tell_host(vb, vb->deflate_vq);
- mutex_unlock(&vb->balloon_lock);
release_pages_balloon(vb);
+ mutex_unlock(&vb->balloon_lock);
return num_freed_pages;
}
{
struct virtqueue *vqs[3];
vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
- const char *names[] = { "inflate", "deflate", "stats" };
+ static const char * const names[] = { "inflate", "deflate", "stats" };
int err, nvqs;
/*
struct virtqueue *vqs[2];
vq_callback_t *cbs[] = { virtinput_recv_events,
virtinput_recv_status };
- static const char *names[] = { "events", "status" };
+ static const char * const names[] = { "events", "status" };
int err;
err = vi->vdev->config->find_vqs(vi->vdev, 2, vqs, cbs, names);
static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[])
+ const char * const names[])
{
struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
unsigned int irq = platform_get_irq(vm_dev->pdev, 0);
static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[],
+ const char * const names[],
bool use_msix,
bool per_vq_vectors)
{
int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[])
+ const char * const names[])
{
int err;
int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[]);
+ const char * const names[]);
const char *vp_bus_name(struct virtio_device *vdev);
/* Setup the affinity for a virtqueue:
static int vp_modern_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[])
+ const char * const names[])
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
struct virtqueue *vq;
/* If we expect an interrupt for the next entry, tell host
* by writing event index and flush out the write before
* the read in the next get_buf call. */
- if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
- vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx);
- virtio_mb(vq->weak_barriers);
- }
+ if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT))
+ virtio_store_mb(vq->weak_barriers,
+ &vring_used_event(&vq->vring),
+ cpu_to_virtio16(_vq->vdev, vq->last_used_idx));
#ifdef DEBUG
vq->last_add_time_valid = false;
}
/* TODO: tune this threshold */
bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4;
- vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs);
- virtio_mb(vq->weak_barriers);
+
+ virtio_store_mb(vq->weak_barriers,
+ &vring_used_event(&vq->vring),
+ cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs));
+
if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) - vq->last_used_idx) > bufs)) {
END_USE(vq);
return false;
#include <linux/percpu.h>
#include <linux/cpu.h>
+#include <asm/barrier.h>
#include <asm/sync_bitops.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
* control block.
*/
if (head == 0) {
- rmb(); /* Ensure word is up-to-date before reading head. */
+ virt_rmb(); /* Ensure word is up-to-date before reading head. */
head = control_block->head[priority];
}
avail = len;
/* Must write data /after/ reading the consumer index. */
- mb();
+ virt_mb();
memcpy(dst, data, avail);
data += avail;
len -= avail;
/* Other side must not see new producer until data is there. */
- wmb();
+ virt_wmb();
intf->req_prod += avail;
/* Implies mb(): other side will see the updated producer. */
avail = len;
/* Must read data /after/ reading the producer index. */
- rmb();
+ virt_rmb();
memcpy(data, src, avail);
data += avail;
len -= avail;
/* Other side must not see free space until we've copied out */
- mb();
+ virt_mb();
intf->rsp_cons += avail;
pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
#define read_barrier_depends() do { } while (0)
#endif
+#ifndef __smp_mb
+#define __smp_mb() mb()
+#endif
+
+#ifndef __smp_rmb
+#define __smp_rmb() rmb()
+#endif
+
+#ifndef __smp_wmb
+#define __smp_wmb() wmb()
+#endif
+
+#ifndef __smp_read_barrier_depends
+#define __smp_read_barrier_depends() read_barrier_depends()
+#endif
+
#ifdef CONFIG_SMP
#ifndef smp_mb
-#define smp_mb() mb()
+#define smp_mb() __smp_mb()
#endif
#ifndef smp_rmb
-#define smp_rmb() rmb()
+#define smp_rmb() __smp_rmb()
#endif
#ifndef smp_wmb
-#define smp_wmb() wmb()
+#define smp_wmb() __smp_wmb()
#endif
#ifndef smp_read_barrier_depends
-#define smp_read_barrier_depends() read_barrier_depends()
+#define smp_read_barrier_depends() __smp_read_barrier_depends()
#endif
#else /* !CONFIG_SMP */
#endif /* CONFIG_SMP */
+#ifndef __smp_store_mb
+#define __smp_store_mb(var, value) do { WRITE_ONCE(var, value); __smp_mb(); } while (0)
+#endif
+
+#ifndef __smp_mb__before_atomic
+#define __smp_mb__before_atomic() __smp_mb()
+#endif
+
+#ifndef __smp_mb__after_atomic
+#define __smp_mb__after_atomic() __smp_mb()
+#endif
+
+#ifndef __smp_store_release
+#define __smp_store_release(p, v) \
+do { \
+ compiletime_assert_atomic_type(*p); \
+ __smp_mb(); \
+ WRITE_ONCE(*p, v); \
+} while (0)
+#endif
+
+#ifndef __smp_load_acquire
+#define __smp_load_acquire(p) \
+({ \
+ typeof(*p) ___p1 = READ_ONCE(*p); \
+ compiletime_assert_atomic_type(*p); \
+ __smp_mb(); \
+ ___p1; \
+})
+#endif
+
+#ifdef CONFIG_SMP
+
+#ifndef smp_store_mb
+#define smp_store_mb(var, value) __smp_store_mb(var, value)
+#endif
+
+#ifndef smp_mb__before_atomic
+#define smp_mb__before_atomic() __smp_mb__before_atomic()
+#endif
+
+#ifndef smp_mb__after_atomic
+#define smp_mb__after_atomic() __smp_mb__after_atomic()
+#endif
+
+#ifndef smp_store_release
+#define smp_store_release(p, v) __smp_store_release(p, v)
+#endif
+
+#ifndef smp_load_acquire
+#define smp_load_acquire(p) __smp_load_acquire(p)
+#endif
+
+#else /* !CONFIG_SMP */
+
#ifndef smp_store_mb
-#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
+#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0)
#endif
#ifndef smp_mb__before_atomic
-#define smp_mb__before_atomic() smp_mb()
+#define smp_mb__before_atomic() barrier()
#endif
#ifndef smp_mb__after_atomic
-#define smp_mb__after_atomic() smp_mb()
+#define smp_mb__after_atomic() barrier()
#endif
+#ifndef smp_store_release
#define smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
- smp_mb(); \
+ barrier(); \
WRITE_ONCE(*p, v); \
} while (0)
+#endif
+#ifndef smp_load_acquire
#define smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
- smp_mb(); \
+ barrier(); \
___p1; \
})
+#endif
+
+#endif
+
+/* Barriers for virtual machine guests when talking to an SMP host */
+#define virt_mb() __smp_mb()
+#define virt_rmb() __smp_rmb()
+#define virt_wmb() __smp_wmb()
+#define virt_read_barrier_depends() __smp_read_barrier_depends()
+#define virt_store_mb(var, value) __smp_store_mb(var, value)
+#define virt_mb__before_atomic() __smp_mb__before_atomic()
+#define virt_mb__after_atomic() __smp_mb__after_atomic()
+#define virt_store_release(p, v) __smp_store_release(p, v)
+#define virt_load_acquire(p) __smp_load_acquire(p)
#endif /* !__ASSEMBLY__ */
#endif /* __ASM_GENERIC_BARRIER_H */
int (*find_vqs)(struct virtio_device *, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
- const char *names[]);
+ const char * const names[]);
void (*del_vqs)(struct virtio_device *);
u64 (*get_features)(struct virtio_device *vdev);
int (*finalize_features)(struct virtio_device *vdev);
* anyone care?
*
* For virtio_pci on SMP, we don't need to order with respect to MMIO
- * accesses through relaxed memory I/O windows, so smp_mb() et al are
+ * accesses through relaxed memory I/O windows, so virt_mb() et al are
* sufficient.
*
* For using virtio to talk to real devices (eg. other heterogeneous
static inline void virtio_mb(bool weak_barriers)
{
-#ifdef CONFIG_SMP
if (weak_barriers)
- smp_mb();
+ virt_mb();
else
-#endif
mb();
}
static inline void virtio_rmb(bool weak_barriers)
{
if (weak_barriers)
- dma_rmb();
+ virt_rmb();
else
rmb();
}
static inline void virtio_wmb(bool weak_barriers)
{
if (weak_barriers)
- dma_wmb();
+ virt_wmb();
else
wmb();
}
+static inline void virtio_store_mb(bool weak_barriers,
+ __virtio16 *p, __virtio16 v)
+{
+ if (weak_barriers) {
+ virt_store_mb(*p, v);
+ } else {
+ WRITE_ONCE(*p, v);
+ mb();
+ }
+}
+
struct virtio_device;
struct virtqueue;
#define RING_PUSH_REQUESTS(_r) do { \
- wmb(); /* back sees requests /before/ updated producer index */ \
+ virt_wmb(); /* back sees requests /before/ updated producer index */ \
(_r)->sring->req_prod = (_r)->req_prod_pvt; \
} while (0)
#define RING_PUSH_RESPONSES(_r) do { \
- wmb(); /* front sees responses /before/ updated producer index */ \
+ virt_wmb(); /* front sees responses /before/ updated producer index */ \
(_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
} while (0)
#define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \
RING_IDX __old = (_r)->sring->req_prod; \
RING_IDX __new = (_r)->req_prod_pvt; \
- wmb(); /* back sees requests /before/ updated producer index */ \
+ virt_wmb(); /* back sees requests /before/ updated producer index */ \
(_r)->sring->req_prod = __new; \
- mb(); /* back sees new requests /before/ we check req_event */ \
+ virt_mb(); /* back sees new requests /before/ we check req_event */ \
(_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
(RING_IDX)(__new - __old)); \
} while (0)
#define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \
RING_IDX __old = (_r)->sring->rsp_prod; \
RING_IDX __new = (_r)->rsp_prod_pvt; \
- wmb(); /* front sees responses /before/ updated producer index */ \
+ virt_wmb(); /* front sees responses /before/ updated producer index */ \
(_r)->sring->rsp_prod = __new; \
- mb(); /* front sees new responses /before/ we check rsp_event */ \
+ virt_mb(); /* front sees new responses /before/ we check rsp_event */ \
(_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
(RING_IDX)(__new - __old)); \
} while (0)
(_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
if (_work_to_do) break; \
(_r)->sring->req_event = (_r)->req_cons + 1; \
- mb(); \
+ virt_mb(); \
(_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
} while (0)
(_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
if (_work_to_do) break; \
(_r)->sring->rsp_event = (_r)->rsp_cons + 1; \
- mb(); \
+ virt_mb(); \
(_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
} while (0)
bool dequeued_page;
dequeued_page = false;
+ spin_lock_irqsave(&b_dev_info->pages_lock, flags);
list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
/*
* Block others from accessing the 'page' while we get around
continue;
}
#endif
- spin_lock_irqsave(&b_dev_info->pages_lock, flags);
balloon_page_delete(page);
__count_vm_event(BALLOON_DEFLATE);
- spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
unlock_page(page);
dequeued_page = true;
break;
}
}
+ spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
if (!dequeued_page) {
/*
}
}
# check for memory barriers without a comment.
- if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) {
+
+ my $barriers = qr{
+ mb|
+ rmb|
+ wmb|
+ read_barrier_depends
+ }x;
+ my $barrier_stems = qr{
+ mb__before_atomic|
+ mb__after_atomic|
+ store_release|
+ load_acquire|
+ store_mb|
+ (?:$barriers)
+ }x;
+ my $all_barriers = qr{
+ (?:$barriers)|
+ smp_(?:$barrier_stems)|
+ virt_(?:$barrier_stems)
+ }x;
+
+ if ($line =~ /\b(?:$all_barriers)\s*\(/) {
if (!ctx_has_comment($first_line, $linenr)) {
WARN("MEMORY_BARRIER",
"memory barrier without comment\n" . $herecurr);
}
}
+ my $underscore_smp_barriers = qr{__smp_(?:$barrier_stems)}x;
+
+ if ($realfile !~ m@^include/asm-generic/@ &&
+ $realfile !~ m@/barrier\.h$@ &&
+ $line =~ m/\b(?:$underscore_smp_barriers)\s*\(/ &&
+ $line !~ m/^.\s*\#\s*define\s+(?:$underscore_smp_barriers)\s*\(/) {
+ WARN("MEMORY_BARRIER",
+ "__smp memory barriers shouldn't be used outside barrier.h and asm-generic\n" . $herecurr);
+ }
+
# check for waitqueue_active without a comment.
if ($line =~ /\bwaitqueue_active\s*\(/) {
if (!ctx_has_comment($first_line, $linenr)) {
projects / cascardo / linux.git / commitdiff