From: Brian Behlendorf Date: Fri, 30 Oct 2009 17:55:25 +0000 (-0700) Subject: Use Linux atomic primitives by default. X-Git-Tag: zfs-0.8.0-rc1~152^2~655 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5e9b5d832b228b0628a61c9c1c9bf0b05d2fe122;p=zfs Use Linux atomic primitives by default. Previously Solaris style atomic primitives were implemented simply by wrapping the desired operation in a global spinlock. This was easy to implement at the time when I wasn't 100% sure I could safely layer the Solaris atomic primatives on the Linux counterparts. It however was likely not good for performance. After more investigation however it does appear the Solaris primitives can be layered on Linux's fairly safely. The Linux atomic_t type really just wraps a long so we can simply cast the Solaris unsigned value to either a atomic_t or atomic64_t. The only lingering problem for both implementations is that Solaris provides no atomic read function. This means reading a 64-bit value on a 32-bit arch can (and will) result in word breaking. I was very concerned about this initially, but upon further reflection it is a limitation of the Solaris API. So really we are just being bug-for-bug compatible here. With this change the default implementation is layered on top of Linux atomic types. However, because we're assuming a lot about the internal implementation of those types I've made it easy to fall-back to the generic approach. Simply build with --enable-atomic_spinlocks if issues are encountered with the new implementation. --- diff --git a/config/spl-build.m4 b/config/spl-build.m4 index e6a626108..15d10841b 100644 --- a/config/spl-build.m4 +++ b/config/spl-build.m4 @@ -25,6 +25,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [ SPL_AC_DEBUG_KMEM SPL_AC_DEBUG_KSTAT SPL_AC_DEBUG_CALLB + SPL_AC_ATOMIC_SPINLOCK SPL_AC_TYPE_UINTPTR_T SPL_AC_TYPE_ATOMIC64_T SPL_AC_3ARGS_INIT_WORK @@ -302,6 +303,27 @@ AC_DEFUN([SPL_AC_DEBUG_CALLB], [ fi ]) +dnl # +dnl # Use the atomic implemenation based on global spinlocks. This +dnl # should never be needed, however it has been left in place as +dnl # a fallback option in case problems are observed with directly +dnl # mapping to the native Linux atomic operations. +dnl # +AC_DEFUN([SPL_AC_ATOMIC_SPINLOCK], [ + AC_ARG_ENABLE([atomic-spinlocks], + [AS_HELP_STRING([--enable-atomic-spinlocks], + [Atomic types use spinlocks @<:@default=no@:>@])], + [], + [enable_atomic_spinlocks=no]) + + AS_IF([test "x$enable_atomic_spinlocks" = xyes], + [AC_DEFINE([ATOMIC_SPINLOCK], [1], + [Atomic types use spinlocks])]) + + AC_MSG_CHECKING([whether atomic types use spinlocks]) + AC_MSG_RESULT([$enable_atomic_spinlocks]) +]) + dnl # dnl # SPL_LINUX_CONFTEST dnl # diff --git a/configure b/configure index 8c8736883..bcbd0fb54 100755 --- a/configure +++ b/configure @@ -1038,6 +1038,8 @@ Optional Features: --enable-debug-kmem Enable kmem debug support (default off) --enable-debug-kstat Enable kstat debug support (default off) --enable-debug-callb Enable callb debug support (default off) + --enable-atomic-spinlocks + Atomic types use spinlocks [default=no] Optional Packages: --with-PACKAGE[=ARG] use PACKAGE [ARG=yes] @@ -3986,7 +3988,7 @@ ia64-*-hpux*) ;; *-*-irix6*) # Find out which ABI we are using. - echo '#line 3989 "configure"' > conftest.$ac_ext + echo '#line 3991 "configure"' > conftest.$ac_ext if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5 (eval $ac_compile) 2>&5 ac_status=$? @@ -5585,7 +5587,7 @@ fi # Provide some information about the compiler. -echo "$as_me:5588:" \ +echo "$as_me:5590:" \ "checking for Fortran 77 compiler version" >&5 ac_compiler=`set X $ac_compile; echo $2` { (eval echo "$as_me:$LINENO: \"$ac_compiler --version &5\"") >&5 @@ -6648,11 +6650,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:6651: $lt_compile\"" >&5) + (eval echo "\"\$as_me:6653: $lt_compile\"" >&5) (eval "$lt_compile" 2>conftest.err) ac_status=$? cat conftest.err >&5 - echo "$as_me:6655: \$? = $ac_status" >&5 + echo "$as_me:6657: \$? = $ac_status" >&5 if (exit $ac_status) && test -s "$ac_outfile"; then # The compiler can only warn and ignore the option if not recognized # So say no if there are warnings other than the usual output. @@ -6916,11 +6918,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:6919: $lt_compile\"" >&5) + (eval echo "\"\$as_me:6921: $lt_compile\"" >&5) (eval "$lt_compile" 2>conftest.err) ac_status=$? cat conftest.err >&5 - echo "$as_me:6923: \$? = $ac_status" >&5 + echo "$as_me:6925: \$? = $ac_status" >&5 if (exit $ac_status) && test -s "$ac_outfile"; then # The compiler can only warn and ignore the option if not recognized # So say no if there are warnings other than the usual output. @@ -7020,11 +7022,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:7023: $lt_compile\"" >&5) + (eval echo "\"\$as_me:7025: $lt_compile\"" >&5) (eval "$lt_compile" 2>out/conftest.err) ac_status=$? cat out/conftest.err >&5 - echo "$as_me:7027: \$? = $ac_status" >&5 + echo "$as_me:7029: \$? = $ac_status" >&5 if (exit $ac_status) && test -s out/conftest2.$ac_objext then # The compiler can only warn and ignore the option if not recognized @@ -8489,7 +8491,7 @@ linux*) libsuff= case "$host_cpu" in x86_64*|s390x*|powerpc64*) - echo '#line 8492 "configure"' > conftest.$ac_ext + echo '#line 8494 "configure"' > conftest.$ac_ext if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5 (eval $ac_compile) 2>&5 ac_status=$? @@ -9386,7 +9388,7 @@ else lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2 lt_status=$lt_dlunknown cat > conftest.$ac_ext < conftest.$ac_ext <&5) + (eval echo "\"\$as_me:11834: $lt_compile\"" >&5) (eval "$lt_compile" 2>conftest.err) ac_status=$? cat conftest.err >&5 - echo "$as_me:11836: \$? = $ac_status" >&5 + echo "$as_me:11838: \$? = $ac_status" >&5 if (exit $ac_status) && test -s "$ac_outfile"; then # The compiler can only warn and ignore the option if not recognized # So say no if there are warnings other than the usual output. @@ -11933,11 +11935,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:11936: $lt_compile\"" >&5) + (eval echo "\"\$as_me:11938: $lt_compile\"" >&5) (eval "$lt_compile" 2>out/conftest.err) ac_status=$? cat out/conftest.err >&5 - echo "$as_me:11940: \$? = $ac_status" >&5 + echo "$as_me:11942: \$? = $ac_status" >&5 if (exit $ac_status) && test -s out/conftest2.$ac_objext then # The compiler can only warn and ignore the option if not recognized @@ -12469,7 +12471,7 @@ linux*) libsuff= case "$host_cpu" in x86_64*|s390x*|powerpc64*) - echo '#line 12472 "configure"' > conftest.$ac_ext + echo '#line 12474 "configure"' > conftest.$ac_ext if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5 (eval $ac_compile) 2>&5 ac_status=$? @@ -13527,11 +13529,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:13530: $lt_compile\"" >&5) + (eval echo "\"\$as_me:13532: $lt_compile\"" >&5) (eval "$lt_compile" 2>conftest.err) ac_status=$? cat conftest.err >&5 - echo "$as_me:13534: \$? = $ac_status" >&5 + echo "$as_me:13536: \$? = $ac_status" >&5 if (exit $ac_status) && test -s "$ac_outfile"; then # The compiler can only warn and ignore the option if not recognized # So say no if there are warnings other than the usual output. @@ -13631,11 +13633,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:13634: $lt_compile\"" >&5) + (eval echo "\"\$as_me:13636: $lt_compile\"" >&5) (eval "$lt_compile" 2>out/conftest.err) ac_status=$? cat out/conftest.err >&5 - echo "$as_me:13638: \$? = $ac_status" >&5 + echo "$as_me:13640: \$? = $ac_status" >&5 if (exit $ac_status) && test -s out/conftest2.$ac_objext then # The compiler can only warn and ignore the option if not recognized @@ -15080,7 +15082,7 @@ linux*) libsuff= case "$host_cpu" in x86_64*|s390x*|powerpc64*) - echo '#line 15083 "configure"' > conftest.$ac_ext + echo '#line 15085 "configure"' > conftest.$ac_ext if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5 (eval $ac_compile) 2>&5 ac_status=$? @@ -15858,11 +15860,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:15861: $lt_compile\"" >&5) + (eval echo "\"\$as_me:15863: $lt_compile\"" >&5) (eval "$lt_compile" 2>conftest.err) ac_status=$? cat conftest.err >&5 - echo "$as_me:15865: \$? = $ac_status" >&5 + echo "$as_me:15867: \$? = $ac_status" >&5 if (exit $ac_status) && test -s "$ac_outfile"; then # The compiler can only warn and ignore the option if not recognized # So say no if there are warnings other than the usual output. @@ -16126,11 +16128,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:16129: $lt_compile\"" >&5) + (eval echo "\"\$as_me:16131: $lt_compile\"" >&5) (eval "$lt_compile" 2>conftest.err) ac_status=$? cat conftest.err >&5 - echo "$as_me:16133: \$? = $ac_status" >&5 + echo "$as_me:16135: \$? = $ac_status" >&5 if (exit $ac_status) && test -s "$ac_outfile"; then # The compiler can only warn and ignore the option if not recognized # So say no if there are warnings other than the usual output. @@ -16230,11 +16232,11 @@ else -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \ -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \ -e 's:$: $lt_compiler_flag:'` - (eval echo "\"\$as_me:16233: $lt_compile\"" >&5) + (eval echo "\"\$as_me:16235: $lt_compile\"" >&5) (eval "$lt_compile" 2>out/conftest.err) ac_status=$? cat out/conftest.err >&5 - echo "$as_me:16237: \$? = $ac_status" >&5 + echo "$as_me:16239: \$? = $ac_status" >&5 if (exit $ac_status) && test -s out/conftest2.$ac_objext then # The compiler can only warn and ignore the option if not recognized @@ -17699,7 +17701,7 @@ linux*) libsuff= case "$host_cpu" in x86_64*|s390x*|powerpc64*) - echo '#line 17702 "configure"' > conftest.$ac_ext + echo '#line 17704 "configure"' > conftest.$ac_ext if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5 (eval $ac_compile) 2>&5 ac_status=$? @@ -19203,6 +19205,29 @@ _ACEOF echo "${ECHO_T}no" >&6 fi + + # Check whether --enable-atomic-spinlocks or --disable-atomic-spinlocks was given. +if test "${enable_atomic_spinlocks+set}" = set; then + enableval="$enable_atomic_spinlocks" + +else + enable_atomic_spinlocks=no +fi; + + if test "x$enable_atomic_spinlocks" = xyes; then + +cat >>confdefs.h <<\_ACEOF +#define ATOMIC_SPINLOCK 1 +_ACEOF + +fi + + + echo "$as_me:$LINENO: checking whether atomic types use spinlocks" >&5 +echo $ECHO_N "checking whether atomic types use spinlocks... $ECHO_C" >&6 + echo "$as_me:$LINENO: result: $enable_atomic_spinlocks" >&5 +echo "${ECHO_T}$enable_atomic_spinlocks" >&6 + echo "$as_me:$LINENO: checking whether kernel defines uintptr_t" >&5 echo $ECHO_N "checking whether kernel defines uintptr_t... $ECHO_C" >&6 @@ -22351,6 +22376,29 @@ _ACEOF echo "${ECHO_T}no" >&6 fi + + # Check whether --enable-atomic-spinlocks or --disable-atomic-spinlocks was given. +if test "${enable_atomic_spinlocks+set}" = set; then + enableval="$enable_atomic_spinlocks" + +else + enable_atomic_spinlocks=no +fi; + + if test "x$enable_atomic_spinlocks" = xyes; then + +cat >>confdefs.h <<\_ACEOF +#define ATOMIC_SPINLOCK 1 +_ACEOF + +fi + + + echo "$as_me:$LINENO: checking whether atomic types use spinlocks" >&5 +echo $ECHO_N "checking whether atomic types use spinlocks... $ECHO_C" >&6 + echo "$as_me:$LINENO: result: $enable_atomic_spinlocks" >&5 +echo "${ECHO_T}$enable_atomic_spinlocks" >&6 + echo "$as_me:$LINENO: checking whether kernel defines uintptr_t" >&5 echo $ECHO_N "checking whether kernel defines uintptr_t... $ECHO_C" >&6 diff --git a/include/sys/atomic.h b/include/sys/atomic.h index cd0eb3b0a..4f4a1e058 100644 --- a/include/sys/atomic.h +++ b/include/sys/atomic.h @@ -27,31 +27,94 @@ #ifndef _SPL_ATOMIC_H #define _SPL_ATOMIC_H -#ifdef __cplusplus -extern "C" { -#endif - #include #include -#include +#include -/* XXX: Serialize everything through global locks. This is - * going to be bad for performance, but for now it's the easiest - * way to ensure correct behavior. I don't like it at all. - * It would be nicer to make these function to the atomic linux - * functions, but the normal uint64_t type complicates this. +/* + * Two approaches to atomic operations are implemented each with its + * own benefits are drawbacks imposed by the Solaris API. Neither + * approach handles the issue of word breaking when using a 64-bit + * atomic variable on a 32-bit arch. The Solaris API would need to + * add an atomic read call to correctly support this. + * + * When ATOMIC_SPINLOCK is defined all atomic operations will be + * serialized through global spin locks. This is bad for performance + * but it does allow a simple generic implementation. + * + * When ATOMIC_SPINLOCK is not defined the Linux atomic operations + * are used. This is safe as long as the core Linux implementation + * doesn't change because we are relying on the fact that an atomic + * type is really just a uint32 or uint64. If this changes at some + * point in the future we need to fall-back to the spin approach. */ -extern spinlock_t atomic64_lock; +#ifdef ATOMIC_SPINLOCK extern spinlock_t atomic32_lock; +extern spinlock_t atomic64_lock; -static __inline__ uint32_t +static __inline__ void +atomic_inc_32(volatile uint32_t *target) +{ + spin_lock(&atomic32_lock); + (*target)++; + spin_unlock(&atomic32_lock); +} + +static __inline__ void +atomic_dec_32(volatile uint32_t *target) +{ + spin_lock(&atomic32_lock); + (*target)--; + spin_unlock(&atomic32_lock); +} + +static __inline__ void atomic_add_32(volatile uint32_t *target, int32_t delta) +{ + spin_lock(&atomic32_lock); + *target += delta; + spin_unlock(&atomic32_lock); +} + +static __inline__ void +atomic_sub_32(volatile uint32_t *target, int32_t delta) +{ + spin_lock(&atomic32_lock); + *target -= delta; + spin_unlock(&atomic32_lock); +} + +static __inline__ uint32_t +atomic_add_32_nv(volatile uint32_t *target, uint32_t delta) +{ + spin_lock(&atomic32_lock); + *target += delta; + spin_unlock(&atomic32_lock); + + return *target; +} + +static __inline__ uint32_t +atomic_sub_32_nv(volatile uint32_t *target, uint32_t delta) +{ + spin_lock(&atomic32_lock); + *target -= delta; + spin_unlock(&atomic32_lock); + + return *target; +} + +static __inline__ uint32_t +atomic_cas_32(volatile uint32_t *target, uint32_t cmp, + uint32_t newval) { uint32_t rc; spin_lock(&atomic32_lock); rc = *target; - *target += delta; + if (*target == cmp) + *target = newval; + spin_unlock(&atomic32_lock); return rc; @@ -73,30 +136,20 @@ atomic_dec_64(volatile uint64_t *target) spin_unlock(&atomic64_lock); } -static __inline__ uint64_t +static __inline__ void atomic_add_64(volatile uint64_t *target, uint64_t delta) { - uint64_t rc; - spin_lock(&atomic64_lock); - rc = *target; *target += delta; spin_unlock(&atomic64_lock); - - return rc; } -static __inline__ uint64_t +static __inline__ void atomic_sub_64(volatile uint64_t *target, uint64_t delta) { - uint64_t rc; - spin_lock(&atomic64_lock); - rc = *target; *target -= delta; spin_unlock(&atomic64_lock); - - return rc; } static __inline__ uint64_t @@ -121,7 +174,7 @@ atomic_sub_64_nv(volatile uint64_t *target, uint64_t delta) static __inline__ uint64_t atomic_cas_64(volatile uint64_t *target, uint64_t cmp, - uint64_t newval) + uint64_t newval) { uint64_t rc; @@ -134,45 +187,40 @@ atomic_cas_64(volatile uint64_t *target, uint64_t cmp, return rc; } -static __inline__ uint32_t -atomic_cas_32(volatile uint32_t *target, uint32_t cmp, - uint32_t newval) -{ - uint32_t rc; - spin_lock(&atomic32_lock); - rc = *target; - if (*target == cmp) - *target = newval; +#else /* ATOMIC_SPINLOCK */ - spin_unlock(&atomic32_lock); +#define atomic_inc_32(v) atomic_inc((atomic_t *)(v)) +#define atomic_dec_32(v) atomic_dec((atomic_t *)(v)) +#define atomic_add_32(v, i) atomic_add((i), (atomic_t *)(v)) +#define atomic_sub_32(v, i) atomic_sub((i), (atomic_t *)(v)) +#define atomic_add_32_nv(v, i) atomic_add_return((i), (atomic_t *)(v)) +#define atomic_sub_32_nv(v, i) atomic_sub_return((i), (atomic_t *)(v)) +#define atomic_cas_32(v, x, y) atomic_cmpxchg((atomic_t *)(v), x, y) +#define atomic_inc_64(v) atomic64_inc((atomic64_t *)(v)) +#define atomic_dec_64(v) atomic64_dec((atomic64_t *)(v)) +#define atomic_add_64(v, i) atomic64_add((i), (atomic64_t *)(v)) +#define atomic_sub_64(v, i) atomic64_sub((i), (atomic64_t *)(v)) +#define atomic_add_64_nv(v, i) atomic64_add_return((i), (atomic64_t *)(v)) +#define atomic_sub_64_nv(v, i) atomic64_sub_return((i), (atomic64_t *)(v)) +#define atomic_cas_64(v, x, y) atomic64_cmpxchg((atomic64_t *)(v), x, y) - return rc; -} +#endif /* ATOMIC_SPINLOCK */ #ifdef _LP64 -/* XXX: Implement atomic_cas_ptr() in terms of uint64'ts. This - * is of course only safe and correct for 64 bit arches... but - * for now I'm OK with that. - */ static __inline__ void * atomic_cas_ptr(volatile void *target, void *cmp, void *newval) { return (void *)atomic_cas_64((volatile uint64_t *)target, (uint64_t)cmp, (uint64_t)newval); } -#else +#else /* _LP64 */ static __inline__ void * atomic_cas_ptr(volatile void *target, void *cmp, void *newval) { return (void *)atomic_cas_32((volatile uint32_t *)target, (uint32_t)cmp, (uint32_t)newval); } -#endif - -#ifdef __cplusplus -} -#endif +#endif /* _LP64 */ #endif /* _SPL_ATOMIC_H */ - diff --git a/module/spl/spl-atomic.c b/module/spl/spl-atomic.c index 40cdb06cc..decf9515e 100644 --- a/module/spl/spl-atomic.c +++ b/module/spl/spl-atomic.c @@ -32,9 +32,11 @@ #define DEBUG_SUBSYSTEM S_ATOMIC +#ifdef ATOMIC_SPINLOCK /* Global atomic lock declarations */ -spinlock_t atomic64_lock = SPIN_LOCK_UNLOCKED; spinlock_t atomic32_lock = SPIN_LOCK_UNLOCKED; +spinlock_t atomic64_lock = SPIN_LOCK_UNLOCKED; -EXPORT_SYMBOL(atomic64_lock); EXPORT_SYMBOL(atomic32_lock); +EXPORT_SYMBOL(atomic64_lock); +#endif /* ATOMIC_SPINLOCK */ diff --git a/spl_config.h.in b/spl_config.h.in index 176da466b..feb09a865 100644 --- a/spl_config.h.in +++ b/spl_config.h.in @@ -1,5 +1,8 @@ /* spl_config.h.in. Generated from configure.ac by autoheader. */ +/* Atomic types use spinlocks */ +#undef ATOMIC_SPINLOCK + /* Define to 1 to enable callb debugging */ #undef DEBUG_CALLB