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The per-thread state is refactored two use two strategies:
1. The default one uses a TLS structure, which will be placed in the
static TLS space (using __thread keyword).
2. Linux allocates via struct pthread and access it through THREAD_*
macros.
The default strategy has the disadvantage of increasing libc.so static
TLS consumption and thus decreasing the possible surplus used in
some scenarios (which might be mitigated by BZ#25051 fix).
It is used only on Hurd, where accessing the thread storage in the in
single thread case is not straightforward (afaiu, Hurd developers could
correct me here).
The fallback static allocation used for allocation failure is also
removed: defining its size is problematic without synchronizing with
translated messages (to avoid partial translation) and the resulting
usage is not thread-safe.
Checked on x86-64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
and s390x-linux-gnu.
Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
414 lines
14 KiB
C
414 lines
14 KiB
C
/* Copyright (C) 2002-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _DESCR_H
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#define _DESCR_H 1
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#include <limits.h>
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#include <sched.h>
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#include <setjmp.h>
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#include <stdbool.h>
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#include <sys/types.h>
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#include <hp-timing.h>
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#include <list_t.h>
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#include <lowlevellock.h>
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#include <pthreaddef.h>
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#include <dl-sysdep.h>
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#include <thread_db.h>
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#include <tls.h>
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#include <unwind.h>
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#include <bits/types/res_state.h>
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#include <kernel-features.h>
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#include <tls-internal-struct.h>
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#ifndef TCB_ALIGNMENT
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# define TCB_ALIGNMENT sizeof (double)
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#endif
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/* We keep thread specific data in a special data structure, a two-level
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array. The top-level array contains pointers to dynamically allocated
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arrays of a certain number of data pointers. So we can implement a
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sparse array. Each dynamic second-level array has
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PTHREAD_KEY_2NDLEVEL_SIZE
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entries. This value shouldn't be too large. */
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#define PTHREAD_KEY_2NDLEVEL_SIZE 32
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/* We need to address PTHREAD_KEYS_MAX key with PTHREAD_KEY_2NDLEVEL_SIZE
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keys in each subarray. */
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#define PTHREAD_KEY_1STLEVEL_SIZE \
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((PTHREAD_KEYS_MAX + PTHREAD_KEY_2NDLEVEL_SIZE - 1) \
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/ PTHREAD_KEY_2NDLEVEL_SIZE)
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/* Internal version of the buffer to store cancellation handler
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information. */
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struct pthread_unwind_buf
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{
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struct
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{
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__jmp_buf jmp_buf;
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int mask_was_saved;
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} cancel_jmp_buf[1];
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union
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{
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/* This is the placeholder of the public version. */
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void *pad[4];
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struct
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{
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/* Pointer to the previous cleanup buffer. */
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struct pthread_unwind_buf *prev;
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/* Backward compatibility: state of the old-style cleanup
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handler at the time of the previous new-style cleanup handler
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installment. */
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struct _pthread_cleanup_buffer *cleanup;
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/* Cancellation type before the push call. */
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int canceltype;
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} data;
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} priv;
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};
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/* Opcodes and data types for communication with the signal handler to
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change user/group IDs. */
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struct xid_command
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{
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int syscall_no;
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long int id[3];
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volatile int cntr;
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volatile int error; /* -1: no call yet, 0: success seen, >0: error seen. */
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};
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/* Data structure used by the kernel to find robust futexes. */
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struct robust_list_head
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{
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void *list;
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long int futex_offset;
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void *list_op_pending;
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};
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/* Data strcture used to handle thread priority protection. */
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struct priority_protection_data
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{
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int priomax;
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unsigned int priomap[];
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};
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/* Thread descriptor data structure. */
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struct pthread
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{
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union
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{
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#if !TLS_DTV_AT_TP
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/* This overlaps the TCB as used for TLS without threads (see tls.h). */
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tcbhead_t header;
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#else
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struct
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{
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/* multiple_threads is enabled either when the process has spawned at
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least one thread or when a single-threaded process cancels itself.
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This enables additional code to introduce locking before doing some
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compare_and_exchange operations and also enable cancellation points.
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The concepts of multiple threads and cancellation points ideally
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should be separate, since it is not necessary for multiple threads to
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have been created for cancellation points to be enabled, as is the
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case is when single-threaded process cancels itself.
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Since enabling multiple_threads enables additional code in
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cancellation points and compare_and_exchange operations, there is a
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potential for an unneeded performance hit when it is enabled in a
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single-threaded, self-canceling process. This is OK though, since a
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single-threaded process will enable async cancellation only when it
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looks to cancel itself and is hence going to end anyway. */
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int multiple_threads;
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int gscope_flag;
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} header;
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#endif
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/* This extra padding has no special purpose, and this structure layout
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is private and subject to change without affecting the official ABI.
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We just have it here in case it might be convenient for some
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implementation-specific instrumentation hack or suchlike. */
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void *__padding[24];
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};
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/* This descriptor's link on the `stack_used' or `__stack_user' list. */
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list_t list;
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/* Thread ID - which is also a 'is this thread descriptor (and
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therefore stack) used' flag. */
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pid_t tid;
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/* Ununsed. */
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pid_t pid_ununsed;
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/* List of robust mutexes the thread is holding. */
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#if __PTHREAD_MUTEX_HAVE_PREV
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void *robust_prev;
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struct robust_list_head robust_head;
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/* The list above is strange. It is basically a double linked list
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but the pointer to the next/previous element of the list points
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in the middle of the object, the __next element. Whenever
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casting to __pthread_list_t we need to adjust the pointer
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first.
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These operations are effectively concurrent code in that the thread
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can get killed at any point in time and the kernel takes over. Thus,
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the __next elements are a kind of concurrent list and we need to
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enforce using compiler barriers that the individual operations happen
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in such a way that the kernel always sees a consistent list. The
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backward links (ie, the __prev elements) are not used by the kernel.
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FIXME We should use relaxed MO atomic operations here and signal fences
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because this kind of concurrency is similar to synchronizing with a
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signal handler. */
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# define QUEUE_PTR_ADJUST (offsetof (__pthread_list_t, __next))
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# define ENQUEUE_MUTEX_BOTH(mutex, val) \
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do { \
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__pthread_list_t *next = (__pthread_list_t *) \
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((((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_head.list)) & ~1ul) \
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- QUEUE_PTR_ADJUST); \
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next->__prev = (void *) &mutex->__data.__list.__next; \
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mutex->__data.__list.__next = THREAD_GETMEM (THREAD_SELF, \
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robust_head.list); \
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mutex->__data.__list.__prev = (void *) &THREAD_SELF->robust_head; \
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/* Ensure that the new list entry is ready before we insert it. */ \
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__asm ("" ::: "memory"); \
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THREAD_SETMEM (THREAD_SELF, robust_head.list, \
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(void *) (((uintptr_t) &mutex->__data.__list.__next) \
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| val)); \
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} while (0)
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# define DEQUEUE_MUTEX(mutex) \
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do { \
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__pthread_list_t *next = (__pthread_list_t *) \
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((char *) (((uintptr_t) mutex->__data.__list.__next) & ~1ul) \
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- QUEUE_PTR_ADJUST); \
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next->__prev = mutex->__data.__list.__prev; \
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__pthread_list_t *prev = (__pthread_list_t *) \
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((char *) (((uintptr_t) mutex->__data.__list.__prev) & ~1ul) \
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- QUEUE_PTR_ADJUST); \
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prev->__next = mutex->__data.__list.__next; \
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/* Ensure that we remove the entry from the list before we change the \
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__next pointer of the entry, which is read by the kernel. */ \
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__asm ("" ::: "memory"); \
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mutex->__data.__list.__prev = NULL; \
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mutex->__data.__list.__next = NULL; \
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} while (0)
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#else
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union
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{
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__pthread_slist_t robust_list;
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struct robust_list_head robust_head;
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};
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# define ENQUEUE_MUTEX_BOTH(mutex, val) \
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do { \
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mutex->__data.__list.__next \
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= THREAD_GETMEM (THREAD_SELF, robust_list.__next); \
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/* Ensure that the new list entry is ready before we insert it. */ \
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__asm ("" ::: "memory"); \
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THREAD_SETMEM (THREAD_SELF, robust_list.__next, \
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(void *) (((uintptr_t) &mutex->__data.__list) | val)); \
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} while (0)
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# define DEQUEUE_MUTEX(mutex) \
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do { \
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__pthread_slist_t *runp = (__pthread_slist_t *) \
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(((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_list.__next)) & ~1ul); \
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if (runp == &mutex->__data.__list) \
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THREAD_SETMEM (THREAD_SELF, robust_list.__next, runp->__next); \
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else \
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{ \
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__pthread_slist_t *next = (__pthread_slist_t *) \
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(((uintptr_t) runp->__next) & ~1ul); \
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while (next != &mutex->__data.__list) \
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{ \
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runp = next; \
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next = (__pthread_slist_t *) (((uintptr_t) runp->__next) & ~1ul); \
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} \
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\
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runp->__next = next->__next; \
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/* Ensure that we remove the entry from the list before we change the \
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__next pointer of the entry, which is read by the kernel. */ \
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__asm ("" ::: "memory"); \
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mutex->__data.__list.__next = NULL; \
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} \
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} while (0)
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#endif
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#define ENQUEUE_MUTEX(mutex) ENQUEUE_MUTEX_BOTH (mutex, 0)
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#define ENQUEUE_MUTEX_PI(mutex) ENQUEUE_MUTEX_BOTH (mutex, 1)
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/* List of cleanup buffers. */
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struct _pthread_cleanup_buffer *cleanup;
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/* Unwind information. */
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struct pthread_unwind_buf *cleanup_jmp_buf;
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#define HAVE_CLEANUP_JMP_BUF
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/* Flags determining processing of cancellation. */
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int cancelhandling;
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/* Bit set if cancellation is disabled. */
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#define CANCELSTATE_BIT 0
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#define CANCELSTATE_BITMASK (0x01 << CANCELSTATE_BIT)
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/* Bit set if asynchronous cancellation mode is selected. */
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#define CANCELTYPE_BIT 1
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#define CANCELTYPE_BITMASK (0x01 << CANCELTYPE_BIT)
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/* Bit set if canceling has been initiated. */
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#define CANCELING_BIT 2
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#define CANCELING_BITMASK (0x01 << CANCELING_BIT)
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/* Bit set if canceled. */
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#define CANCELED_BIT 3
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#define CANCELED_BITMASK (0x01 << CANCELED_BIT)
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/* Bit set if thread is exiting. */
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#define EXITING_BIT 4
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#define EXITING_BITMASK (0x01 << EXITING_BIT)
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/* Bit set if thread terminated and TCB is freed. */
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#define TERMINATED_BIT 5
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#define TERMINATED_BITMASK (0x01 << TERMINATED_BIT)
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/* Bit set if thread is supposed to change XID. */
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#define SETXID_BIT 6
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#define SETXID_BITMASK (0x01 << SETXID_BIT)
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/* Mask for the rest. Helps the compiler to optimize. */
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#define CANCEL_RESTMASK 0xffffff80
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#define CANCEL_ENABLED_AND_CANCELED(value) \
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(((value) & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK \
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| CANCEL_RESTMASK | TERMINATED_BITMASK)) == CANCELED_BITMASK)
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#define CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS(value) \
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(((value) & (CANCELSTATE_BITMASK | CANCELTYPE_BITMASK | CANCELED_BITMASK \
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| EXITING_BITMASK | CANCEL_RESTMASK | TERMINATED_BITMASK)) \
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== (CANCELTYPE_BITMASK | CANCELED_BITMASK))
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/* Flags. Including those copied from the thread attribute. */
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int flags;
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/* We allocate one block of references here. This should be enough
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to avoid allocating any memory dynamically for most applications. */
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struct pthread_key_data
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{
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/* Sequence number. We use uintptr_t to not require padding on
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32- and 64-bit machines. On 64-bit machines it helps to avoid
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wrapping, too. */
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uintptr_t seq;
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/* Data pointer. */
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void *data;
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} specific_1stblock[PTHREAD_KEY_2NDLEVEL_SIZE];
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/* Two-level array for the thread-specific data. */
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struct pthread_key_data *specific[PTHREAD_KEY_1STLEVEL_SIZE];
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/* Flag which is set when specific data is set. */
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bool specific_used;
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/* True if events must be reported. */
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bool report_events;
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/* True if the user provided the stack. */
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bool user_stack;
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/* True if thread must stop at startup time. */
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bool stopped_start;
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/* Formerly used for dealing with cancellation. */
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int parent_cancelhandling_unsed;
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/* Lock to synchronize access to the descriptor. */
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int lock;
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/* Lock for synchronizing setxid calls. */
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unsigned int setxid_futex;
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#if HP_TIMING_INLINE
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hp_timing_t cpuclock_offset_ununsed;
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#endif
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/* If the thread waits to join another one the ID of the latter is
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stored here.
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In case a thread is detached this field contains a pointer of the
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TCB if the thread itself. This is something which cannot happen
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in normal operation. */
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struct pthread *joinid;
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/* Check whether a thread is detached. */
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#define IS_DETACHED(pd) ((pd)->joinid == (pd))
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/* The result of the thread function. */
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void *result;
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/* Scheduling parameters for the new thread. */
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struct sched_param schedparam;
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int schedpolicy;
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/* Start position of the code to be executed and the argument passed
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to the function. */
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void *(*start_routine) (void *);
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void *arg;
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/* Debug state. */
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td_eventbuf_t eventbuf;
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/* Next descriptor with a pending event. */
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struct pthread *nextevent;
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/* Machine-specific unwind info. */
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struct _Unwind_Exception exc;
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/* If nonzero, pointer to the area allocated for the stack and guard. */
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void *stackblock;
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/* Size of the stackblock area including the guard. */
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size_t stackblock_size;
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/* Size of the included guard area. */
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size_t guardsize;
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/* This is what the user specified and what we will report. */
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size_t reported_guardsize;
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/* Thread Priority Protection data. */
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struct priority_protection_data *tpp;
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/* Resolver state. */
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struct __res_state res;
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/* Signal mask for the new thread. Used during thread startup to
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restore the signal mask. (Threads are launched with all signals
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masked.) */
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sigset_t sigmask;
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/* Indicates whether is a C11 thread created by thrd_creat. */
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bool c11;
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/* Used on strsignal. */
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struct tls_internal_t tls_state;
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/* This member must be last. */
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char end_padding[];
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#define PTHREAD_STRUCT_END_PADDING \
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(sizeof (struct pthread) - offsetof (struct pthread, end_padding))
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} __attribute ((aligned (TCB_ALIGNMENT)));
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#endif /* descr.h */
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