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Diffstat (limited to 'storage/xtradb/include/os0once.h')
-rw-r--r-- | storage/xtradb/include/os0once.h | 125 |
1 files changed, 0 insertions, 125 deletions
diff --git a/storage/xtradb/include/os0once.h b/storage/xtradb/include/os0once.h deleted file mode 100644 index a8bbaf1d2d4..00000000000 --- a/storage/xtradb/include/os0once.h +++ /dev/null @@ -1,125 +0,0 @@ -/***************************************************************************** - -Copyright (c) 2014, Oracle and/or its affiliates. All Rights Reserved. - -This program is free software; you can redistribute it and/or modify it under -the terms of the GNU General Public License as published by the Free Software -Foundation; version 2 of the License. - -This program 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 General Public License for more details. - -You should have received a copy of the GNU General Public License along with -this program; if not, write to the Free Software Foundation, Inc., -51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA - -*****************************************************************************/ - -/**************************************************//** -@file include/os0once.h -A class that aids executing a given function exactly once in a multi-threaded -environment. - -Created Feb 20, 2014 Vasil Dimov -*******************************************************/ - -#ifndef os0once_h -#define os0once_h - -#include "univ.i" - -#include "os0sync.h" -#include "ut0ut.h" - -/** Execute a given function exactly once in a multi-threaded environment -or wait for the function to be executed by another thread. - -Example usage: -First the user must create a control variable of type os_once::state_t and -assign it os_once::NEVER_DONE. -Then the user must pass this variable, together with a function to be -executed to os_once::do_or_wait_for_done(). - -Multiple threads can call os_once::do_or_wait_for_done() simultaneously with -the same (os_once::state_t) control variable. The provided function will be -called exactly once and when os_once::do_or_wait_for_done() returns then this -function has completed execution, by this or another thread. In other words -os_once::do_or_wait_for_done() will either execute the provided function or -will wait for its execution to complete if it is already called by another -thread or will do nothing if the function has already completed its execution -earlier. - -This mimics pthread_once(3), but unfortunatelly pthread_once(3) does not -support passing arguments to the init_routine() function. We should use -std::call_once() when we start compiling with C++11 enabled. */ -class os_once { -public: - /** Control variables' state type */ - typedef ib_uint32_t state_t; - - /** Not yet executed. */ - static const state_t NEVER_DONE = 0; - - /** Currently being executed by this or another thread. */ - static const state_t IN_PROGRESS = 1; - - /** Finished execution. */ - static const state_t DONE = 2; - -#ifdef HAVE_ATOMIC_BUILTINS - /** Call a given function or wait its execution to complete if it is - already called by another thread. - @param[in,out] state control variable - @param[in] do_func function to call - @param[in,out] do_func_arg an argument to pass to do_func(). */ - static - void - do_or_wait_for_done( - volatile state_t* state, - void (*do_func)(void*), - void* do_func_arg) - { - /* Avoid calling os_compare_and_swap_uint32() in the most - common case. */ - if (*state == DONE) { - return; - } - - if (os_compare_and_swap_uint32(state, - NEVER_DONE, IN_PROGRESS)) { - /* We are the first. Call the function. */ - - do_func(do_func_arg); - - const bool swapped = os_compare_and_swap_uint32( - state, IN_PROGRESS, DONE); - - ut_a(swapped); - } else { - /* The state is not NEVER_DONE, so either it is - IN_PROGRESS (somebody is calling the function right - now or DONE (it has already been called and completed). - Wait for it to become DONE. */ - for (;;) { - const state_t s = *state; - - switch (s) { - case DONE: - return; - case IN_PROGRESS: - break; - case NEVER_DONE: - /* fall through */ - default: - ut_error; - } - - UT_RELAX_CPU(); - } - } - } -#endif /* HAVE_ATOMIC_BUILTINS */ -}; - -#endif /* os0once_h */ |