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Diffstat (limited to 'winsup/cygwin/sync.cc')
| -rw-r--r-- | winsup/cygwin/sync.cc | 152 |
1 files changed, 0 insertions, 152 deletions
diff --git a/winsup/cygwin/sync.cc b/winsup/cygwin/sync.cc deleted file mode 100644 index 6bd0ecf66..000000000 --- a/winsup/cygwin/sync.cc +++ /dev/null @@ -1,152 +0,0 @@ -/* sync.cc: Synchronization functions for cygwin. - - This file implements the methods for controlling the "muto" class - which is intended to operate similarly to a mutex but attempts to - avoid making expensive calls to the kernel. - - Copyright 2000, 2001, 2002, 2003, 2004, 2005 Red Hat, Inc. - - Written by Christopher Faylor <cgf@cygnus.com> - -This file is part of Cygwin. - -This software is a copyrighted work licensed under the terms of the -Cygwin license. Please consult the file "CYGWIN_LICENSE" for -details. */ - -#include "winsup.h" -#include "miscfuncs.h" -#include "sync.h" -#include "thread.h" -#include "cygtls.h" - -#undef WaitForSingleObject - -DWORD NO_COPY muto::exiting_thread; - -void -muto::grab () -{ - tls = &_my_tls; -} - -/* Constructor */ -muto * -muto::init (const char *s) -{ - char *already_exists = (char *) InterlockedExchangePointer (&name, s); - if (already_exists) - while (!bruteforce) - low_priority_sleep (0); - else - { - waiters = -1; - /* Create event which is used in the fallback case when blocking is necessary */ - bruteforce = CreateEvent (&sec_none_nih, FALSE, FALSE, NULL); - if (!bruteforce) - api_fatal ("couldn't allocate muto '%s', %E", s); - } - - return this; -} - -#if 0 /* FIXME: Do we need this? mutos aren't destroyed until process exit */ -/* Destructor (racy?) */ -muto::~muto () -{ - while (visits) - release (); - - HANDLE h = bruteforce; - bruteforce = NULL; - /* Just need to close the event handle */ - if (h) - CloseHandle (h); -} -#endif - -/* Acquire the lock. Argument is the number of milliseconds to wait for - the lock. Multiple visits from the same thread are allowed and should - be handled correctly. - - Note: The goal here is to minimize, as much as possible, calls to the - OS. Hence the use of InterlockedIncrement, etc., rather than (much) more - expensive OS mutexes. Also note that the only two valid "ms" times are - 0 and INFINITE. */ -int -muto::acquire (DWORD ms) -{ - void *this_tls = &_my_tls; -#if 0 - if (exiting_thread) - return this_tid == exiting_thread; -#endif - - if (tls != this_tls) - { - /* Increment the waiters part of the class. Need to do this first to - avoid potential races. */ - LONG was_waiting = ms ? InterlockedIncrement (&waiters) : 0; - - while (was_waiting || InterlockedExchange (&sync, 1) != 0) - switch (WaitForSingleObject (bruteforce, ms)) - { - case WAIT_OBJECT_0: - was_waiting = 0; - break; - default: - return 0; /* failed. */ - } - - /* Have to do it this way to avoid a race */ - if (!ms) - InterlockedIncrement (&waiters); - - tls = this_tls; /* register this thread. */ - } - - return ++visits; /* Increment visit count. */ -} - -bool -muto::acquired () -{ - return tls == &_my_tls; -} - -/* Return the muto lock. Needs to be called once per every acquire. */ -int -muto::release () -{ - void *this_tls = &_my_tls; - - if (tls != this_tls || !visits) - { - SetLastError (ERROR_NOT_OWNER); /* Didn't have the lock. */ - return 0; /* failed. */ - } - - /* FIXME: Need to check that other thread has not exited, too. */ - if (!--visits) - { - tls = 0; /* We were the last unlocker. */ - InterlockedExchange (&sync, 0); /* Reset trigger. */ - /* This thread had incremented waiters but had never decremented it. - Decrement it now. If it is >= 0 then there are possibly other - threads waiting for the lock, so trigger bruteforce. */ - if (InterlockedDecrement (&waiters) >= 0) - SetEvent (bruteforce); /* Wake up one of the waiting threads */ - else if (*name == '!') - { - CloseHandle (bruteforce); /* If *name == '!' and there are no - other waiters, then this is the - last time this muto will ever be - used, so close the handle. */ -#ifdef DEBUGGING - bruteforce = NULL; -#endif - } - } - - return 1; /* success. */ -} |