No. Neither is correct. Spinlocks should be used to protect data, not code. Therefore you should be protecting the kernel data structures, not kernel code paths. You need a spinlock for each piece of data that might be shared. You need to design your kernel data structures so that sharing is minimised because, in practice, contended spinlocks kill performance.Megan65 wrote:yes
i implement spin-locks in my OS.
using same lock for all system calls and scheduler or spreate spinlocks for any system call?
sorry for my bad english
Code: Select all
// semaphore_down
void semaphore_down( semaphore_t* _sem )
{
spin_lock( &_sem->lock );
_sem->res_count--;
if ( _sem->res_count < 0 )
{
queue_push( _sem->queue, (void*)g_pCurTask );
spin_unlock( &_sem->lock );
change_task_state( g_pCurTask, ETS_BLOCKED );
switch_task();
return;
}
spin_unlock( &_sem->lock );
}Why did you waste time (of Berkus and I) by not saying that in the first post ?my problem is in implementing semaphores and mutexes
sorryWhy did you waste time (of Berkus and I) by not saying that in the first post ?
my semaphores implementation can not protect critical regions. i don't understand where is problem. can u check my code (about two months i work on it but i cant find problem):The code looks okay to me. I'm not sure I understand your problem.
Code: Select all
// semaphore_down
void semaphore_down( semaphore_t* _sem )
{
spin_lock( &_sem->lock );
_sem->res_count--;
if ( _sem->res_count < 0 )
{
queue_push( _sem->queue, (void*)g_pCurTask );
spin_unlock( &_sem->lock );
/*** Another CPU could unblock this task here, before it has blocked. This ***/
/*** would lead to deadlock (tasks waiting for something that they already have) ***/
change_task_state( g_pCurTask, ETS_BLOCKED );
switch_task();
return;
}
spin_unlock( &_sem->lock );
}Code: Select all
// semaphore_down
void semaphore_down( semaphore_t* _sem )
{
spin_lock( &_sem->lock );
_sem->res_count--;
if ( _sem->res_count < 0 )
{
queue_push( _sem->queue, (void*)g_pCurTask );
spin_lock( &scheduler_lock );
spin_unlock( &_sem->lock );
change_task_state( g_pCurTask, ETS_BLOCKED );
switch_task_and_unlock_scheduler_lock();
return;
}
spin_unlock( &_sem->lock );
}Code: Select all
// semaphore_down
void semaphore_down( semaphore_t* _sem )
{
spin_lock( &_sem->lock );
_sem->res_count--;
if ( _sem->res_count < 0 )
{
queue_push( _sem->queue, (void*)g_pCurTask );
change_task_state( g_pCurTask, ETS_BLOCKED );
switch_task_and_unlock( &_sem->lock );
return;
}
spin_unlock( &_sem->lock );
}
