| /* |
| * Copyright (C) 2017 The Android Open Source Project |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
| * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include"private/bionic_futex.h" |
| |
| #include<stdatomic.h> |
| #include<time.h> |
| |
| #include"private/bionic_time_conversions.h" |
| |
| staticinline __always_inlineintFutexWithTimeout(volatilevoid* ftx,int op,int value, |
| bool use_realtime_clock, |
| const timespec* abs_timeout,intbitset){ |
| // pthread's and semaphore's default behavior is to use CLOCK_REALTIME, however this behavior is |
| // essentially never intended, as that clock is prone to change discontinuously. |
| // |
| // What users really intend is to use CLOCK_MONOTONIC, however only pthread_cond_timedwait() |
| // provides this as an option and even there, a large amount of existing code does not opt into |
| // CLOCK_MONOTONIC. |
| // |
| // We have seen numerous bugs directly attributable to this difference. Therefore, we provide |
| // this general workaround to always use CLOCK_MONOTONIC for waiting, regardless of what the input |
| // timespec is. |
| timespec converted_timeout; |
| if(abs_timeout){ |
| if((op& FUTEX_CMD_MASK)== FUTEX_LOCK_PI){ |
| if(!use_realtime_clock){ |
| realtime_time_from_monotonic_time(converted_timeout,*abs_timeout); |
| abs_timeout=&converted_timeout; |
| } |
| }else{ |
| op&=~FUTEX_CLOCK_REALTIME; |
| if(use_realtime_clock){ |
| monotonic_time_from_realtime_time(converted_timeout,*abs_timeout); |
| abs_timeout=&converted_timeout; |
| } |
| } |
| if(abs_timeout->tv_sec<0){ |
| return-ETIMEDOUT; |
| } |
| } |
| |
| return __futex(ftx, op, value, abs_timeout,bitset); |
| } |
| |
| int __futex_wait_ex(volatilevoid* ftx,bool shared,int value,bool use_realtime_clock, |
| const timespec* abs_timeout){ |
| returnFutexWithTimeout(ftx,(shared? FUTEX_WAIT_BITSET: FUTEX_WAIT_BITSET_PRIVATE), value, |
| use_realtime_clock, abs_timeout, FUTEX_BITSET_MATCH_ANY); |
| } |
| |
| int __futex_pi_lock_ex(volatilevoid* ftx,bool shared,bool use_realtime_clock, |
| const timespec* abs_timeout){ |
| // We really want FUTEX_LOCK_PI2 which is default CLOCK_MONOTONIC, but that isn't supported |
| // on linux before 5.14. FUTEX_LOCK_PI uses CLOCK_REALTIME. Here we verify support. |
| |
| static atomic_int lock_op=0; |
| int op= atomic_load_explicit(&lock_op, memory_order_relaxed); |
| if(op==0){ |
| uint32_t tmp=0; |
| if(__futex(&tmp, FUTEX_LOCK_PI2,0,nullptr,0)==0){ |
| __futex(&tmp, FUTEX_UNLOCK_PI,0,nullptr,0); |
| op= FUTEX_LOCK_PI2; |
| }else{ |
| op= FUTEX_LOCK_PI; |
| } |
| atomic_store_explicit(&lock_op, op, memory_order_relaxed); |
| } |
| |
| if(!shared) op|= FUTEX_PRIVATE_FLAG; |
| returnFutexWithTimeout(ftx, op,0/* value */, use_realtime_clock, abs_timeout,0/* bitset */); |
| } |
