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pthread: remove use of private Native_config API

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Former Native_config::context_area_virtual_base() was used to identify
the main, which is not desired as the Native_config is rather low-level
(almost private to the base libs). The commit uses a library constructor
to retrieve the main-thread Thread_base pointer, which can be used later
to distinguish main and other threads.
This commit is contained in:
Christian Helmuth 2015-12-04 12:36:08 +01:00
parent ee4619687b
commit 30e129a91b
1 changed files with 42 additions and 31 deletions
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73
repos/libports/src/lib/pthread/thread.cc
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@ -44,6 +44,19 @@ static Lock pthread_cleanup_list_lock;
static List<thread_cleanup> pthread_cleanup_list; static List<thread_cleanup> pthread_cleanup_list;
/*
* We initialize the main-thread pointer in a constructor depending on the
* assumption that libpthread is loaded on application startup by ldso. During
* this stage only the main thread is executed.
*/
static __attribute__((constructor)) Thread_base * main_thread()
{
static Thread_base *thread = Thread_base::myself();
return thread;
}
extern "C" { extern "C" {
/* Thread */ /* Thread */
@ -105,6 +118,13 @@ extern "C" {
} }
/* special non-POSIX function (for example used in libresolv) */
int _pthread_main_np(void)
{
return (Thread_base::myself() == main_thread());
}
pthread_t pthread_self(void) pthread_t pthread_self(void)
{ {
Thread_base *myself = Thread_base::myself(); Thread_base *myself = Thread_base::myself();
@ -113,37 +133,34 @@ extern "C" {
if (pthread) if (pthread)
return pthread; return pthread;
/* either it is the main thread, an alien thread or a bug */ /*
* We pass here if the main thread or an alien thread calls
* pthread_self(). So check for aliens (or other bugs) and opt-out
* early.
*/
/* determine name of thread */ if (!_pthread_main_np()) {
char name[Thread_base::Context::NAME_LEN]; char name[Thread_base::Context::NAME_LEN];
myself->name(name, sizeof(name)); myself->name(name, sizeof(name));
/* determine if stack is in first context area slot */ PERR("pthread_self() called from alien thread named '%s'", name);
addr_t stack = reinterpret_cast<addr_t>(&myself);
bool is_main = Native_config::context_area_virtual_base() <= stack &&
stack < Native_config::context_area_virtual_base() +
Native_config::context_virtual_size();
/* check that stack and name is of main thread */ return nullptr;
if (is_main && !strcmp(name, "main")) {
/* create a pthread object containing copy of main Thread_base */
static struct pthread_attr main_thread_attr;
static struct pthread *main = nullptr;
if (!main) {
/*
* The pthread object does not get deleted, because this would
* also delete the 'Thread_base' of the main thread.
*/
main = new (Genode::env()->heap()) struct pthread(*myself, &main_thread_attr);
}
return main;
} }
PERR("pthread_self() called from alien thread named '%s'", name); /*
* We create a pthread object containing a copy of main thread's
* Thread_base object. Therefore, we ensure the pthread object does not
* get deleted by allocating it in heap via new(). Otherwise, the
* static destruction of the pthread object would also destruct the
* 'Thread_base' of the main thread.
*/
return nullptr; static struct pthread_attr main_thread_attr;
static struct pthread *main = new (Genode::env()->heap())
struct pthread(*myself, &main_thread_attr);
return main;
} }
@ -182,12 +199,6 @@ extern "C" {
} }
int _pthread_main_np(void)
{
return (Thread_base::myself() == 0);
}
/* Mutex */ /* Mutex */