Date: Tue, 18 Sep 2012 20:00:48 +0100 From: Attilio Rao <attilio@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Davide Italiano <davide@freebsd.org>, src-committers@freebsd.org, John Baldwin <jhb@freebsd.org>, Jeff Roberson <jeff@freebsd.org>, Dimitry Andric <dim@freebsd.org>, svn-src-projects@freebsd.org Subject: Re: svn commit: r238907 - projects/calloutng/sys/kern Message-ID: <CAJ-FndCmg-GdTf9FWQGZPYB-iGuEt-JH8HrCL%2BwaOqJ%2B8ZUbHQ@mail.gmail.com> In-Reply-To: <CAJ-FndAXw6zjXr=zB3gAVQDKUV_K4=SF39iYQQOV23NkfJ=MPw@mail.gmail.com> References: <201207301350.q6UDobCI099069@svn.freebsd.org> <CAJ-FndBj8tpC_BJXs_RH8sG2TBG8yA=Lxu3-GTVT9Ap_zOCuVQ@mail.gmail.com> <CAJ-FndDnO7wjnWPV0tTu%2BUGHjsxa3YDarMxmyei3ZmjLAFvRkQ@mail.gmail.com> <201207301732.33474.jhb@freebsd.org> <CAJ-FndD5EO12xsWOAe6u0EvX00q33wxO4OivnGjzj0=T2Oe8uA@mail.gmail.com> <CAJ-FndCRg0UCThFkatp=tw7rUWWCvhsApLE=iztLpxpGBC1F9w@mail.gmail.com> <20120918083324.GX37286@deviant.kiev.zoral.com.ua> <CAJ-FndAXw6zjXr=zB3gAVQDKUV_K4=SF39iYQQOV23NkfJ=MPw@mail.gmail.com>
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On Tue, Sep 18, 2012 at 4:30 PM, Attilio Rao <attilio@freebsd.org> wrote:
> On 9/18/12, Konstantin Belousov <kostikbel@gmail.com> wrote:
>> On Tue, Sep 18, 2012 at 01:13:08AM +0100, Attilio Rao wrote:
>>> diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
>>> index 8224672..fc6a75f 100644
>>> --- a/sys/sys/cdefs.h
>>> +++ b/sys/sys/cdefs.h
>>> @@ -114,6 +114,13 @@
>>> #endif
>>>
>>> /*
>>> + * Compiler memory barriers, specific to gcc and clang.
>>> + */
>>> +#if defined(__GNUC__)
>>> +#define __compiler_membar() __asm __volatile(" " : : :
>>> "memory")
>>> +#endif
>>> +
>>> +/*
>>
>> Traditionally, we do provide the fallback for non-GNUC compilers, by
>> defining extern function with the compatible signature. In this case,
>> the empty function just works for the purpose, although with higher
>> overhead than the GNUC case.
>
> I agree, we need a fallback here. Unfortunately I'm buried with job
> stuff but I will provide an errata patch ASAP.
Here is the patch. I didn't use a real extern function body for it,
but just went with an empty macro.
Attilio
Index: sys/sparc64/include/atomic.h
===================================================================
--- sys/sparc64/include/atomic.h (revisione 240672)
+++ sys/sparc64/include/atomic.h (copia locale)
@@ -97,7 +97,7 @@
#define atomic_cas_acq(p, e, s, sz) ({
\
itype(sz) v; \
v = atomic_cas((p), (e), (s), sz); \
- __asm __volatile("" : : : "memory"); \
+ __compiler_membar(); \
v; \
})
@@ -122,7 +122,7 @@
#define atomic_op_acq(p, op, v, sz) ({
\
itype(sz) t; \
t = atomic_op((p), op, (v), sz); \
- __asm __volatile("" : : : "memory"); \
+ __compiler_membar(); \
t; \
})
@@ -139,7 +139,7 @@
#define atomic_load_acq(p, sz) ({
\
itype(sz) v; \
v = atomic_load((p), sz); \
- __asm __volatile("" : : : "memory"); \
+ __compiler_membar(); \
v; \
})
Index: sys/pc98/include/bus.h
===================================================================
--- sys/pc98/include/bus.h (revisione 240672)
+++ sys/pc98/include/bus.h (copia locale)
@@ -593,7 +593,7 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_h
if (flags & BUS_SPACE_BARRIER_READ)
__asm __volatile("lock; addl $0,0(%%esp)" : : : "memory");
else
- __asm __volatile("" : : : "memory");
+ __compiler_membar();
}
#ifdef BUS_SPACE_NO_LEGACY
Index: sys/i386/include/atomic.h
===================================================================
--- sys/i386/include/atomic.h (revisione 240672)
+++ sys/i386/include/atomic.h (copia locale)
@@ -296,7 +296,7 @@ atomic_fetchadd_int(volatile u_int *p, u_int v)
static __inline void \
atomic_store_rel_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
{ \
- __asm __volatile("" : : : "memory"); \
+ __compiler_membar(); \
*p = v; \
} \
struct __hack
@@ -310,7 +310,7 @@ atomic_load_acq_##TYPE(volatile u_##TYPE *p)
\
u_##TYPE tmp; \
\
tmp = *p; \
- __asm __volatile("" : : : "memory"); \
+ __compiler_membar(); \
return (tmp); \
} \
struct __hack
Index: sys/amd64/include/atomic.h
===================================================================
--- sys/amd64/include/atomic.h (revisione 240672)
+++ sys/amd64/include/atomic.h (copia locale)
@@ -226,7 +226,7 @@ atomic_fetchadd_long(volatile u_long *p, u_long v)
static __inline void \
atomic_store_rel_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
{ \
- __asm __volatile("" : : : "memory"); \
+ __compiler_membar(); \
*p = v; \
} \
struct __hack
@@ -240,7 +240,7 @@ atomic_load_acq_##TYPE(volatile u_##TYPE *p)
\
u_##TYPE tmp; \
\
tmp = *p; \
- __asm __volatile("" : : : "memory"); \
+ __compiler_membar(); \
return (tmp); \
} \
struct __hack
Index: sys/sys/cdefs.h
===================================================================
--- sys/sys/cdefs.h (revisione 240672)
+++ sys/sys/cdefs.h (copia locale)
@@ -487,6 +487,15 @@
#define __GLOBL1(sym) __asm__(".globl " #sym)
#define __GLOBL(sym) __GLOBL1(sym)
+/*
+ * Compiler memory barriers, specific to gcc and clang.
+ */
+#if defined(__GNUC__)
+#define __compiler_membar() __asm __volatile(" " : : : "memory")
+#else
+#define __compiler_membar() struct __hack
+#endif
+
#if defined(__GNUC__) || defined(__INTEL_COMPILER)
#define __IDSTRING(name,string) __asm__(".ident\t\"" string "\"")
#else
Index: sys/gnu/fs/xfs/FreeBSD/xfs_freebsd.h
===================================================================
--- sys/gnu/fs/xfs/FreeBSD/xfs_freebsd.h (revisione 240672)
+++ sys/gnu/fs/xfs/FreeBSD/xfs_freebsd.h (copia locale)
@@ -162,7 +162,7 @@
*/
#define EFSCORRUPTED 990 /* Filesystem is corrupted */
-#define SYNCHRONIZE() barrier()
+#define SYNCHRONIZE() __compiler_membar()
#define __return_address __builtin_return_address(0)
/*
Index: sys/gnu/fs/xfs/FreeBSD/xfs_compat.h
===================================================================
--- sys/gnu/fs/xfs/FreeBSD/xfs_compat.h (revisione 240672)
+++ sys/gnu/fs/xfs/FreeBSD/xfs_compat.h (copia locale)
@@ -129,10 +129,6 @@ typedef dev_t os_dev_t;
#define copy_from_user(dst, src, len) copyin((src), (dst), (len))
#endif
-#ifndef barrier
-#define barrier() __asm__ __volatile__("": : :"memory")
-#endif
-
/*
* Map simple global vairables to FreeBSD kernel equivalents
*/
Index: sys/kern/kern_rmlock.c
===================================================================
--- sys/kern/kern_rmlock.c (revisione 240672)
+++ sys/kern/kern_rmlock.c (copia locale)
@@ -65,10 +65,6 @@ __FBSDID("$FreeBSD$");
* does not seem very useful
*/
-static __inline void compiler_memory_barrier(void) {
- __asm __volatile("":::"memory");
-}
-
static void assert_rm(const struct lock_object *lock, int what);
static void lock_rm(struct lock_object *lock, int how);
#ifdef KDTRACE_HOOKS
@@ -353,7 +349,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker
td->td_critnest++; /* critical_enter(); */
- compiler_memory_barrier();
+ __compiler_membar();
pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
@@ -361,7 +357,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker
sched_pin();
- compiler_memory_barrier();
+ __compiler_membar();
td->td_critnest--;
Index: sys/mips/include/cpufunc.h
===================================================================
--- sys/mips/include/cpufunc.h (revisione 240672)
+++ sys/mips/include/cpufunc.h (copia locale)
@@ -70,7 +70,7 @@ static __inline void
mips_barrier(void)
{
#if defined(CPU_CNMIPS) || defined(CPU_RMI) || defined(CPU_NLM)
- __asm __volatile("" : : : "memory");
+ __compiler_membar();
#else
__asm __volatile (".set noreorder\n\t"
"nop\n\t"
Index: sys/x86/include/bus.h
===================================================================
--- sys/x86/include/bus.h (revisione 240672)
+++ sys/x86/include/bus.h (copia locale)
@@ -1014,7 +1014,7 @@ bus_space_barrier(bus_space_tag_t tag __unused, bu
__asm __volatile("lock; addl $0,0(%%esp)" : : : "memory");
#endif
else
- __asm __volatile("" : : : "memory");
+ __compiler_membar();
#endif
}
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