X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=include%2Furcu%2Fstatic%2Furcu-signal.h;fp=include%2Furcu%2Fstatic%2Furcu-signal.h;h=385e6f5d5559c5ca6ca7c70858f15425ddd2f732;hb=4477a87021ffbfbfdb2a2084d05a084171343d36;hp=0000000000000000000000000000000000000000;hpb=5bbe95bb510534d0a5bab8d7d205b32d6e4a57b2;p=urcu.git diff --git a/include/urcu/static/urcu-signal.h b/include/urcu/static/urcu-signal.h new file mode 100644 index 0000000..385e6f5 --- /dev/null +++ b/include/urcu/static/urcu-signal.h @@ -0,0 +1,165 @@ +#ifndef _URCU_SIGNAL_STATIC_H +#define _URCU_SIGNAL_STATIC_H + +/* + * urcu-signal-static.h + * + * Userspace RCU header. + * + * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU + * RELEASE. See urcu.h for linking dynamically with the userspace rcu library. + * + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. + */ + +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#ifdef __cplusplus +extern "C" { +#endif + +/* + * This code section can only be included in LGPL 2.1 compatible source code. + * See below for the function call wrappers which can be used in code meant to + * be only linked with the Userspace RCU library. This comes with a small + * performance degradation on the read-side due to the added function calls. + * This is required to permit relinking with newer versions of the library. + */ + +/* + * The signal number used by the RCU library can be overridden with + * -DSIGRCU= when compiling the library. + * Provide backward compatibility for liburcu 0.3.x SIGURCU. + */ +#ifdef SIGURCU +#define SIGRCU SIGURCU +#endif + +#ifndef SIGRCU +#define SIGRCU SIGUSR1 +#endif + +extern struct urcu_gp urcu_signal_gp; + +extern DECLARE_URCU_TLS(struct urcu_reader, urcu_signal_reader); + +/* + * Helper for _rcu_read_lock(). The format of urcu_signal_gp.ctr (as well as + * the per-thread rcu_reader.ctr) has the upper bits containing a count of + * _rcu_read_lock() nesting, and a lower-order bit that contains either zero + * or URCU_GP_CTR_PHASE. The cmm_barrier() ensures that the accesses in + * _rcu_read_lock() happen before the subsequent read-side critical section. + */ +static inline void _urcu_signal_read_lock_update(unsigned long tmp) +{ + if (caa_likely(!(tmp & URCU_GP_CTR_NEST_MASK))) { + _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, _CMM_LOAD_SHARED(urcu_signal_gp.ctr)); + cmm_barrier(); + } else + _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp + URCU_GP_COUNT); +} + +/* + * Enter an RCU read-side critical section. + * + * The first cmm_barrier() call ensures that the compiler does not reorder + * the body of _rcu_read_lock() with a mutex. + * + * This function and its helper are both less than 10 lines long. The + * intent is that this function meets the 10-line criterion in LGPL, + * allowing this function to be invoked directly from non-LGPL code. + */ +static inline void _urcu_signal_read_lock(void) +{ + unsigned long tmp; + + urcu_assert(URCU_TLS(urcu_signal_reader).registered); + cmm_barrier(); + tmp = URCU_TLS(urcu_signal_reader).ctr; + urcu_assert((tmp & URCU_GP_CTR_NEST_MASK) != URCU_GP_CTR_NEST_MASK); + _urcu_signal_read_lock_update(tmp); +} + +/* + * This is a helper function for _rcu_read_unlock(). + * + * The first cmm_barrier() call ensures that the critical section is + * seen to precede the store to rcu_reader.ctr. + * The second cmm_barrier() call ensures that we write to rcu_reader.ctr + * before reading the update-side futex. + */ +static inline void _urcu_signal_read_unlock_update_and_wakeup(unsigned long tmp) +{ + if (caa_likely((tmp & URCU_GP_CTR_NEST_MASK) == URCU_GP_COUNT)) { + cmm_barrier(); + _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp - URCU_GP_COUNT); + cmm_barrier(); + urcu_common_wake_up_gp(&urcu_signal_gp); + } else + _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp - URCU_GP_COUNT); +} + +/* + * Exit an RCU read-side crtical section. Both this function and its + * helper are smaller than 10 lines of code, and are intended to be + * usable by non-LGPL code, as called out in LGPL. + */ +static inline void _urcu_signal_read_unlock(void) +{ + unsigned long tmp; + + urcu_assert(URCU_TLS(urcu_signal_reader).registered); + tmp = URCU_TLS(urcu_signal_reader).ctr; + urcu_assert(tmp & URCU_GP_CTR_NEST_MASK); + _urcu_signal_read_unlock_update_and_wakeup(tmp); + cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ +} + +/* + * Returns whether within a RCU read-side critical section. + * + * This function is less than 10 lines long. The intent is that this + * function meets the 10-line criterion for LGPL, allowing this function + * to be invoked directly from non-LGPL code. + */ +static inline int _urcu_signal_read_ongoing(void) +{ + return URCU_TLS(urcu_signal_reader).ctr & URCU_GP_CTR_NEST_MASK; +} + +#ifdef __cplusplus +} +#endif + +#endif /* _URCU_SIGNAL_STATIC_H */