This moves all the public POSIX semaphore functions into libc and with
this most of the user-space logic is also moved; namely cancel point and
errno handling.
This also removes the need for the _SEM_XX macros used to differentiate
which API is used per user-/kernel mode. Such macros are henceforth
unnecessary.
This moves task / thread cancel point logic from the NuttX kernel into
libc, while the data needed by the cancel point logic is moved to TLS.
The change is an enabler to move user-space APIs to libc as well, for
a coherent user/kernel separation.
1. add lib_fork api in libs/libc, we need a fork() api to implement the
fork relative method, such as pthread_atfork
2. rename the assembly fork entry function name to up_fork(), and rename
the up_fork() to arch specific name, such as
sim_fork()/arm_fork()/mips_fork() etc.
Signed-off-by: guoshichao <guoshichao@xiaomi.com>
1. as we can use fork to implement vfork, so we rename the vfork to
fork, and use the fork method as the base to implement vfork method
2. create the vfork function as a libc function based on fork
function
Signed-off-by: guoshichao <guoshichao@xiaomi.com>
If cancellation points are enabled, then the following logic is activated in sem_wait(). This causes ECANCELED to be returned every time that sem_wait is called.
int sem_wait(FAR sem_t *sem)
{
...
/* sem_wait() is a cancellation point */
if (enter_cancellation_point())
{
#ifdef CONFIG_CANCELLATION_POINTS
/* If there is a pending cancellation, then do not perform
* the wait. Exit now with ECANCELED.
*/
errcode = ECANCELED;
goto errout_with_cancelpt;
#endif
}
...
Normally this works fine. sem_wait() is the OS API called by the application and will cancel the thread just before it returns to the application. Since it is cancellation point, it should never be called from within the OS.
There there is is one perverse cases where sem_wait() may be nested within another cancellation point. If open() is called, it will attempt to lock a VFS data structure and will eventually call nxmutex_lock(). nxmutex_lock() waits on a semaphore:
int nxmutex_lock(FAR mutex_t *mutex)
{
...
for (; ; )
{
/* Take the semaphore (perhaps waiting) */
ret = _SEM_WAIT(&mutex->sem);
if (ret >= 0)
{
mutex->holder = _SCHED_GETTID();
break;
}
ret = _SEM_ERRVAL(ret);
if (ret != -EINTR && ret != -ECANCELED)
{
break;
}
}
...
}
In the FLAT build, _SEM_WAIT expands to sem_wait(). That causes the error in the logic: It should always expand to nxsem_wait(). That is because sem_wait() is cancellation point and should never be called from with the OS or the C library internally.
The failure occurs because the cancellation point logic in sem_wait() returns -ECANCELED (via _SEM_ERRVAL) because sem_wait() is nested; it needs to return the -ECANCELED error to the outermost cancellation point which is open() in this case. Returning -ECANCELED then causes an infinite loop to occur in nxmutex_lock().
The correct behavior in this case is to call nxsem_wait() instead of sem_wait(). nxsem_wait() is identical to sem_wait() except that it is not a cancelation point. It will return -ECANCELED if the thread is canceled, but only once. So no infinite loop results.
In addition, an nxsem_wait() system call was added to support the call from nxmutex_lock().
This resolves Issue #9695
CURRENT_REGS may change during assert handling, so pass
in the 'regs' parameter at the entry point of _assert.
Signed-off-by: zhangyuan21 <zhangyuan21@xiaomi.com>
The current implementation requires the use of enter_critical_section, so the source code needs to be moved to kernel space
Signed-off-by: hujun5 <hujun5@xiaomi.com>
This is preparation for flushing streams from user space, like it should
be done.
- Move tg_streamlist (group, kernel space) ->
ta_streamlist (TLS, user space)
- Access stream list via tg_info in kernel
- Access stream list via TLS in user space
- Remove / rename nxsched_get_streams -> lib_getstreams
- Remove system call for nxsched_get_streams
I had a link problem regarding prctl while CONFIG_TASK_NAME_SIZE was
defined 0 and building in protected mode. Turns out in monolithic
build prctl is present no matter what CONFIG_TASK_NAME_SIZE, but in
protected mode build its only present if CONFIG_TASK_NAME_SIZE > 0.
So, bring protected mode build in sync with the monolithic one.
Signed-off-by: Michael Jung <michael.jung@secore.ly>
Deleting a task from another task's context will not do, so shut
this gate down for BUILD_KERNEL. In this case if a task wants another
task to terminate, it must ask the other task to politely kill itself.
Note: kthreads still need this, also, the kernel can delete a task
without asking.
Now that the environment strings are stored as an array of strings,
they can be passed from the application via char **environ, which
is really defined as a function call to get_environ_ptr().
This works as is for flat build, but protected mode and kernel mode
require a call gate, which is added here.
