libc/src/__support/threads/identifier.h

   1 //===--- Thread Identifier Header --------------------------------*- C++-*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_IDENTIFIER_H
  10 #define LLVM_LIBC_SRC___SUPPORT_THREADS_IDENTIFIER_H
  11
  12 #ifdef LIBC_FULL_BUILD
  13 #include "src/__support/threads/thread.h"
  14 #endif // LIBC_FULL_BUILD
  15
  16 #include "hdr/types/pid_t.h"
  17 #include "src/__support/OSUtil/syscall.h"
  18 #include "src/__support/macros/optimization.h"
  19 #include <sys/syscall.h>
  20
  21 namespace LIBC_NAMESPACE_DECL {
  22 namespace internal {
  23
  24 LIBC_INLINE pid_t *get_tid_cache() {
  25 #ifdef LIBC_FULL_BUILD
  26   return &self.attrib->tid;
  27 #else
  28   // in non-full build mode, we do not control the fork routine. Therefore,
  29   // we do not cache tid at all.
  30   return nullptr;
  31 #endif
  32 }
  33
  34 LIBC_INLINE pid_t gettid() {
  35   pid_t *cache = get_tid_cache();
  36   if (LIBC_UNLIKELY(!cache || *cache <= 0))
  37     return syscall_impl<pid_t>(SYS_gettid);
  38   return *cache;
  39 }
  40
  41 LIBC_INLINE void force_set_tid(pid_t tid) {
  42   pid_t *cache = get_tid_cache();
  43   if (cache)
  44     *cache = tid;
  45 }
  46
  47 } // namespace internal
  48 } // namespace LIBC_NAMESPACE_DECL
  49
  50 #endif // LLVM_LIBC_SRC___SUPPORT_THREADS_IDENTIFIER_H