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Diffstat (limited to 'tests/windows-tls.c')
| -rw-r--r-- | tests/windows-tls.c | 339 |
1 files changed, 339 insertions, 0 deletions
diff --git a/tests/windows-tls.c b/tests/windows-tls.c new file mode 100644 index 0000000..b24a7d5 --- /dev/null +++ b/tests/windows-tls.c @@ -0,0 +1,339 @@ +/* Thread-local storage (native Windows implementation). + Copyright (C) 2005-2022 Free Software Foundation, Inc. + + This file 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 file 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 program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Bruno Haible <bruno@clisp.org>, 2005. */ + +#include <config.h> + +/* Specification. */ +#include "windows-tls.h" + +#include <errno.h> +#include <limits.h> +#include <stdlib.h> + +#include "windows-once.h" + +void * +glwthread_tls_get (glwthread_tls_key_t key) +{ + return TlsGetValue (key); +} + +int +glwthread_tls_set (glwthread_tls_key_t key, void *value) +{ + if (!TlsSetValue (key, value)) + return EINVAL; + return 0; +} + +/* The following variables keep track of TLS keys with non-NULL destructor. */ + +static glwthread_once_t dtor_table_init_once = GLWTHREAD_ONCE_INIT; + +static CRITICAL_SECTION dtor_table_lock; + +struct dtor { glwthread_tls_key_t key; void (*destructor) (void *); }; + +/* The table of dtors. */ +static struct dtor *dtor_table; +/* Number of active entries in the dtor_table. */ +static unsigned int dtors_count; +/* Valid indices into dtor_table are 0..dtors_used-1. */ +static unsigned int dtors_used; +/* Allocation size of dtor_table. */ +static unsigned int dtors_allocated; +/* Invariant: 0 <= dtors_count <= dtors_used <= dtors_allocated. */ + +/* Number of threads that are currently processing destructors. */ +static unsigned int dtor_processing_threads; + +static void +dtor_table_initialize (void) +{ + InitializeCriticalSection (&dtor_table_lock); + /* The other variables are already initialized to NULL or 0, respectively. */ +} + +static void +dtor_table_ensure_initialized (void) +{ + glwthread_once (&dtor_table_init_once, dtor_table_initialize); +} + +/* Shrinks dtors_used down to dtors_count, by replacing inactive entries + with active ones. */ +static void +dtor_table_shrink_used (void) +{ + unsigned int i = 0; + unsigned int j = dtors_used; + + for (;;) + { + BOOL i_found = FALSE; + BOOL j_found = FALSE; + /* Find the next inactive entry, from the left. */ + for (; i < dtors_count;) + { + if (dtor_table[i].destructor == NULL) + { + i_found = TRUE; + break; + } + i++; + } + + /* Find the next active entry, from the right. */ + for (; j > dtors_count;) + { + j--; + if (dtor_table[j].destructor != NULL) + { + j_found = TRUE; + break; + } + } + + if (i_found != j_found) + /* dtors_count was apparently wrong. */ + abort (); + + if (!i_found) + break; + + /* i_found and j_found are TRUE. Swap the two entries. */ + dtor_table[i] = dtor_table[j]; + + i++; + } + + dtors_used = dtors_count; +} + +void +glwthread_tls_process_destructors (void) +{ + unsigned int repeat; + + dtor_table_ensure_initialized (); + + EnterCriticalSection (&dtor_table_lock); + if (dtor_processing_threads == 0) + { + /* Now it's the appropriate time for shrinking dtors_used. */ + if (dtors_used > dtors_count) + dtor_table_shrink_used (); + } + dtor_processing_threads++; + + for (repeat = GLWTHREAD_DESTRUCTOR_ITERATIONS; repeat > 0; repeat--) + { + unsigned int destructors_run = 0; + + /* Iterate across dtor_table. We don't need to make a copy of dtor_table, + because + * When another thread calls glwthread_tls_key_create with a non-NULL + destructor argument, this will possibly reallocate the dtor_table + array and increase dtors_allocated as well as dtors_used and + dtors_count, but it will not change dtors_used nor the contents of + the first dtors_used entries of dtor_table. + * When another thread calls glwthread_tls_key_delete, this will + possibly set some 'destructor' member to NULL, thus marking an + entry as inactive, but it will not otherwise change dtors_used nor + the contents of the first dtors_used entries of dtor_table. */ + unsigned int i_limit = dtors_used; + unsigned int i; + + for (i = 0; i < i_limit; i++) + { + struct dtor current = dtor_table[i]; + if (current.destructor != NULL) + { + /* The current dtor has not been deleted yet. */ + void *current_value = glwthread_tls_get (current.key); + if (current_value != NULL) + { + /* The current value is non-NULL. Run the destructor. */ + glwthread_tls_set (current.key, NULL); + LeaveCriticalSection (&dtor_table_lock); + current.destructor (current_value); + EnterCriticalSection (&dtor_table_lock); + destructors_run++; + } + } + } + + /* When all TLS values were already NULL, no further iterations are + needed. */ + if (destructors_run == 0) + break; + } + + dtor_processing_threads--; + LeaveCriticalSection (&dtor_table_lock); +} + +int +glwthread_tls_key_create (glwthread_tls_key_t *keyp, void (*destructor) (void *)) +{ + if (destructor != NULL) + { + dtor_table_ensure_initialized (); + + EnterCriticalSection (&dtor_table_lock); + if (dtor_processing_threads == 0) + { + /* Now it's the appropriate time for shrinking dtors_used. */ + if (dtors_used > dtors_count) + dtor_table_shrink_used (); + } + + while (dtors_used == dtors_allocated) + { + /* Need to grow the dtor_table. */ + unsigned int new_allocated = 2 * dtors_allocated + 1; + if (new_allocated < 7) + new_allocated = 7; + if (new_allocated <= dtors_allocated) /* overflow? */ + new_allocated = UINT_MAX; + + LeaveCriticalSection (&dtor_table_lock); + { + struct dtor *new_table = + (struct dtor *) malloc (new_allocated * sizeof (struct dtor)); + if (new_table == NULL) + return ENOMEM; + EnterCriticalSection (&dtor_table_lock); + /* Attention! dtors_used, dtors_allocated may have changed! */ + if (dtors_used < new_allocated) + { + if (dtors_allocated < new_allocated) + { + /* The new_table is useful. */ + memcpy (new_table, dtor_table, + dtors_used * sizeof (struct dtor)); + dtor_table = new_table; + dtors_allocated = new_allocated; + } + else + { + /* The new_table is not useful, since another thread + meanwhile allocated a drop_table that is at least + as large. */ + free (new_table); + } + break; + } + /* The new_table is not useful, since other threads increased + dtors_used. Free it any retry. */ + free (new_table); + } + } + /* Here dtors_used < dtors_allocated. */ + { + /* Allocate a new key. */ + glwthread_tls_key_t key = TlsAlloc (); + if (key == (DWORD)-1) + { + LeaveCriticalSection (&dtor_table_lock); + return EAGAIN; + } + /* Store the new dtor in the dtor_table, after all used entries. + Do not overwrite inactive entries with indices < dtors_used, in order + not to disturb glwthread_tls_process_destructors invocations that may + be executing in other threads. */ + dtor_table[dtors_used].key = key; + dtor_table[dtors_used].destructor = destructor; + dtors_used++; + dtors_count++; + LeaveCriticalSection (&dtor_table_lock); + *keyp = key; + } + } + else + { + /* Allocate a new key. */ + glwthread_tls_key_t key = TlsAlloc (); + if (key == (DWORD)-1) + return EAGAIN; + *keyp = key; + } + return 0; +} + +int +glwthread_tls_key_delete (glwthread_tls_key_t key) +{ + /* Should the destructor be called for all threads that are currently running? + Probably not, because + - ISO C does not specify when the destructor is to be invoked at all. + - In POSIX, the destructor functions specified with pthread_key_create() + are invoked at thread exit. + - It would be hard to implement, because there are no primitives for + accessing thread-specific values from a different thread. */ + dtor_table_ensure_initialized (); + + EnterCriticalSection (&dtor_table_lock); + if (dtor_processing_threads == 0) + { + /* Now it's the appropriate time for shrinking dtors_used. */ + if (dtors_used > dtors_count) + dtor_table_shrink_used (); + /* Here dtors_used == dtors_count. */ + + /* Find the key in dtor_table. */ + { + unsigned int i_limit = dtors_used; + unsigned int i; + + for (i = 0; i < i_limit; i++) + if (dtor_table[i].key == key) + { + if (i < dtors_used - 1) + /* Swap the entries i and dtors_used - 1. */ + dtor_table[i] = dtor_table[dtors_used - 1]; + dtors_count = dtors_used = dtors_used - 1; + break; + } + } + } + else + { + /* Be careful not to disturb the glwthread_tls_process_destructors + invocations that are executing in other threads. */ + unsigned int i_limit = dtors_used; + unsigned int i; + + for (i = 0; i < i_limit; i++) + if (dtor_table[i].destructor != NULL /* skip inactive entries */ + && dtor_table[i].key == key) + { + /* Mark this entry as inactive. */ + dtor_table[i].destructor = NULL; + dtors_count = dtors_count - 1; + break; + } + } + LeaveCriticalSection (&dtor_table_lock); + /* Now we have ensured that glwthread_tls_process_destructors will no longer + use this key. */ + + if (!TlsFree (key)) + return EINVAL; + return 0; +} |