libc/src/pthread/pthread_create.cpp

   1 //===-- Linux implementation of the pthread_create function ---------------===//
   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 #include "pthread_create.h"
  10
  11 #include "pthread_attr_destroy.h"
  12 #include "pthread_attr_init.h"
  13
  14 #include "pthread_attr_getdetachstate.h"
  15 #include "pthread_attr_getguardsize.h"
  16 #include "pthread_attr_getstack.h"
  17
  18 #include "src/__support/common.h"
  19 #include "src/__support/macros/optimization.h"
  20 #include "src/__support/threads/thread.h"
  21
  22 #include <errno.h>
  23 #include <pthread.h> // For pthread_* type definitions.
  24
  25 namespace LIBC_NAMESPACE {
  26
  27 static_assert(sizeof(pthread_t) == sizeof(LIBC_NAMESPACE::Thread),
  28               "Mismatch between pthread_t and internal Thread.");
  29
  30 LLVM_LIBC_FUNCTION(int, pthread_create,
  31                    (pthread_t *__restrict th,
  32                     const pthread_attr_t *__restrict attr,
  33                     __pthread_start_t func, void *arg)) {
  34   pthread_attr_t default_attr;
  35   if (attr == nullptr) {
  36     // We failed to initialize attributes (should be impossible)
  37     if (LIBC_UNLIKELY(LIBC_NAMESPACE::pthread_attr_init(&default_attr) != 0))
  38       return EINVAL;
  39
  40     attr = &default_attr;
  41   }
  42
  43   void *stack;
  44   size_t stacksize, guardsize;
  45   int detachstate;
  46
  47   // As of writing this all the `pthread_attr_get*` functions always succeed.
  48   if (LIBC_UNLIKELY(
  49           LIBC_NAMESPACE::pthread_attr_getstack(attr, &stack, &stacksize) != 0))
  50     return EINVAL;
  51
  52   if (LIBC_UNLIKELY(
  53           LIBC_NAMESPACE::pthread_attr_getguardsize(attr, &guardsize) != 0))
  54     return EINVAL;
  55
  56   if (LIBC_UNLIKELY(
  57           LIBC_NAMESPACE::pthread_attr_getdetachstate(attr, &detachstate) != 0))
  58     return EINVAL;
  59
  60   if (attr == &default_attr)
  61     // Should we fail here? Its non-issue as the moment as pthread_attr_destroy
  62     // can only succeed.
  63     if (LIBC_UNLIKELY(LIBC_NAMESPACE::pthread_attr_destroy(&default_attr) != 0))
  64       return EINVAL;
  65
  66   if (stacksize && stacksize < PTHREAD_STACK_MIN)
  67     return EINVAL;
  68
  69   if (guardsize % EXEC_PAGESIZE != 0)
  70     return EINVAL;
  71
  72   if (detachstate != PTHREAD_CREATE_DETACHED &&
  73       detachstate != PTHREAD_CREATE_JOINABLE)
  74     return EINVAL;
  75
  76   // Thread::run will check validity of the `stack` argument (stack alignment is
  77   // universal, not sure a pthread requirement).
  78
  79   auto *thread = reinterpret_cast<LIBC_NAMESPACE::Thread *>(th);
  80   int result = thread->run(func, arg, stack, stacksize, guardsize,
  81                            detachstate == PTHREAD_CREATE_DETACHED);
  82   if (result != 0 && result != EPERM && result != EINVAL)
  83     return EAGAIN;
  84   return result;
  85 }
  86
  87 } // namespace LIBC_NAMESPACE