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/* Copyright (C) 2002-2022 Free Software Foundation, Inc.
Contributed by Zack Weinberg <zack@codesourcery.com>
This file is part of GCC.
GCC 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; either version 3, or (at your option) any later
version.
GCC 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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* Threads compatibility routines for libgcc2 for VxWorks.
These are out-of-line routines called from gthr-vxworks.h.
This file provides the TLS related support routines, calling specific
VxWorks kernel entry points for this purpose. */
#include "tconfig.h"
#include "tsystem.h"
#include "gthr.h"
#if defined(__GTHREADS)
#include <vxWorks.h>
#ifndef __RTP__
#include <vxLib.h>
#endif
#include <taskLib.h>
#ifndef __RTP__
#include <taskHookLib.h>
#else
#include <errno.h>
#endif
#include <_vxworks-versions.h>
/* Thread-local storage.
A gthread TLS key is simply an offset in an array, the address of which
we store in a single pointer field associated with the current task.
On VxWorks 7, we have direct support for __thread variables and use
such a variable as the pointer "field". On other versions, we resort
to __gthread_get_tls_data and __gthread_set_tls_data functions provided
by the kernel.
There is also a global array which records which keys are valid and
which have destructors.
A task delete hook is installed to execute key destructors. The routines
__gthread_enter_tls_dtor_context and __gthread_leave_tls_dtor_context,
which are also provided by the kernel, ensure that it is safe to call
free() on memory allocated by the task being deleted. This is a no-op on
VxWorks 5, but a major undertaking on AE.
The task delete hook is only installed when at least one thread
has TLS data. This is a necessary precaution, to allow this module
to be unloaded - a module with a hook can not be removed.
Since this interface is used to allocate only a small number of
keys, the table size is small and static, which simplifies the
code quite a bit. Revisit this if and when it becomes necessary. */
#define MAX_KEYS 4
/* This is the structure pointed to by the pointer returned
by __gthread_get_tls_data. */
struct tls_data
{
int *owner;
void *values[MAX_KEYS];
unsigned int generation[MAX_KEYS];
};
/* To make sure we only delete TLS data associated with this object,
include a pointer to a local variable in the TLS data object. */
static int self_owner;
/* Flag to check whether the delete hook is installed. Once installed
it is only removed when unloading this module. */
static volatile int delete_hook_installed;
/* TLS data access internal API. A straight __thread variable starting with
VxWorks 7, a pointer returned by kernel provided routines otherwise. And
on VxWorks 6, the kernel expects us to notify entry/exit of regions
handling such variables by calls to kernel provided __gthread routines. */
#if _VXWORKS_MAJOR_GE(7)
static __thread struct tls_data *__gthread_tls_data;
#define VX_GET_TLS_DATA() __gthread_tls_data
#define VX_SET_TLS_DATA(x) __gthread_tls_data = (x)
#else
extern void *__gthread_get_tls_data (void);
extern void __gthread_set_tls_data (void *data);
#define VX_GET_TLS_DATA() __gthread_get_tls_data()
#define VX_SET_TLS_DATA(x) __gthread_set_tls_data(x)
#endif
#if _VXWORKS_MAJOR_EQ(6)
extern void __gthread_enter_tls_dtor_context (void);
extern void __gthread_leave_tls_dtor_context (void);
#define VX_ENTER_TLS_DTOR() __gthread_enter_tls_dtor_context ()
#define VX_LEAVE_TLS_DTOR() __gthread_leave_tls_dtor_context ()
#else
#define VX_ENTER_TLS_DTOR()
#define VX_LEAVE_TLS_DTOR()
#endif
/* This is a global structure which records all of the active keys.
A key is potentially valid (i.e. has been handed out by
__gthread_key_create) iff its generation count in this structure is
even. In that case, the matching entry in the dtors array is a
routine to be called when a thread terminates with a valid,
non-NULL specific value for that key.
A key is actually valid in a thread T iff the generation count
stored in this structure is equal to the generation count stored in
T's specific-value structure. */
typedef void (*tls_dtor) (void *);
struct tls_keys
{
tls_dtor dtor[MAX_KEYS];
unsigned int generation[MAX_KEYS];
};
#define KEY_VALID_P(key) !(tls_keys.generation[key] & 1)
/* Note: if MAX_KEYS is increased, this initializer must be updated
to match. All the generation counts begin at 1, which means no
key is valid. */
static struct tls_keys tls_keys =
{
{ NULL, NULL, NULL, NULL },
{ 1, 1, 1, 1 }
};
/* This lock protects the tls_keys structure. */
static __gthread_mutex_t tls_lock;
static __gthread_once_t tls_init_guard = __GTHREAD_ONCE_INIT;
/* Internal routines. */
/* The task TCB has just been deleted. Call the destructor
function for each TLS key that has both a destructor and
a non-NULL specific value in this thread.
This routine does not need to take tls_lock; the generation
count protects us from calling a stale destructor. It does
need to read tls_keys.dtor[key] atomically. */
void
tls_delete_hook (void *tcb ATTRIBUTE_UNUSED)
{
struct tls_data *data;
__gthread_key_t key;
data = VX_GET_TLS_DATA();
if (data && data->owner == &self_owner)
{
VX_ENTER_TLS_DTOR();
for (key = 0; key < MAX_KEYS; key++)
{
if (data->generation[key] == tls_keys.generation[key])
{
tls_dtor dtor = tls_keys.dtor[key];
if (dtor)
dtor (data->values[key]);
}
}
free (data);
VX_LEAVE_TLS_DTOR();
VX_SET_TLS_DATA(NULL);
}
}
/* Initialize global data used by the TLS system. */
static void
tls_init (void)
{
__GTHREAD_MUTEX_INIT_FUNCTION (&tls_lock);
}
static void tls_destructor (void) __attribute__ ((destructor));
static void
tls_destructor (void)
{
#ifdef __RTP__
/* All threads but this one should have exited by now. */
tls_delete_hook (NULL);
#endif
/* Unregister the hook. */
if (delete_hook_installed)
taskDeleteHookDelete ((FUNCPTR)tls_delete_hook);
if (tls_init_guard.done && __gthread_mutex_lock (&tls_lock) != ERROR)
semDelete (tls_lock);
}
/* External interface */
/* Store in KEYP a value which can be passed to __gthread_setspecific/
__gthread_getspecific to store and retrieve a value which is
specific to each calling thread. If DTOR is not NULL, it will be
called when a thread terminates with a non-NULL specific value for
this key, with the value as its sole argument. */
int
__gthread_key_create (__gthread_key_t *keyp, tls_dtor dtor)
{
__gthread_key_t key;
__gthread_once (&tls_init_guard, tls_init);
if (__gthread_mutex_lock (&tls_lock) == ERROR)
return errno;
for (key = 0; key < MAX_KEYS; key++)
if (!KEY_VALID_P (key))
goto found_slot;
/* no room */
__gthread_mutex_unlock (&tls_lock);
return EAGAIN;
found_slot:
tls_keys.generation[key]++; /* making it even */
tls_keys.dtor[key] = dtor;
*keyp = key;
__gthread_mutex_unlock (&tls_lock);
return 0;
}
/* Invalidate KEY; it can no longer be used as an argument to
setspecific/getspecific. Note that this does NOT call destructor
functions for any live values for this key. */
int
__gthread_key_delete (__gthread_key_t key)
{
if (key >= MAX_KEYS)
return EINVAL;
__gthread_once (&tls_init_guard, tls_init);
if (__gthread_mutex_lock (&tls_lock) == ERROR)
return errno;
if (!KEY_VALID_P (key))
{
__gthread_mutex_unlock (&tls_lock);
return EINVAL;
}
tls_keys.generation[key]++; /* making it odd */
tls_keys.dtor[key] = 0;
__gthread_mutex_unlock (&tls_lock);
return 0;
}
/* Retrieve the thread-specific value for KEY. If it has never been
set in this thread, or KEY is invalid, returns NULL.
It does not matter if this function races with key_create or
key_delete; the worst that can happen is you get a value other than
the one that a serialized implementation would have provided. */
void *
__gthread_getspecific (__gthread_key_t key)
{
struct tls_data *data;
if (key >= MAX_KEYS)
return 0;
data = VX_GET_TLS_DATA();
if (!data)
return 0;
if (data->generation[key] != tls_keys.generation[key])
return 0;
return data->values[key];
}
/* Set the thread-specific value for KEY. If KEY is invalid, or
memory allocation fails, returns -1, otherwise 0.
The generation count protects this function against races with
key_create/key_delete; the worst thing that can happen is that a
value is successfully stored into a dead generation (and then
immediately becomes invalid). However, we do have to make sure
to read tls_keys.generation[key] atomically. */
int
__gthread_setspecific (__gthread_key_t key, void *value)
{
struct tls_data *data;
unsigned int generation;
if (key >= MAX_KEYS)
return EINVAL;
data = VX_GET_TLS_DATA();
if (!data)
{
if (!delete_hook_installed)
{
/* Install the delete hook. */
if (__gthread_mutex_lock (&tls_lock) == ERROR)
return ENOMEM;
if (!delete_hook_installed)
{
taskDeleteHookAdd ((FUNCPTR)tls_delete_hook);
delete_hook_installed = 1;
}
__gthread_mutex_unlock (&tls_lock);
}
data = malloc (sizeof (struct tls_data));
if (!data)
return ENOMEM;
memset (data, 0, sizeof (struct tls_data));
data->owner = &self_owner;
VX_SET_TLS_DATA(data);
}
generation = tls_keys.generation[key];
if (generation & 1)
return EINVAL;
data->generation[key] = generation;
data->values[key] = value;
return 0;
}
#endif /* __GTHREADS */
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