| 126 | | The destruction of a thread T running in cluster K can be caused by the thread itself, with the pthread_exit() system call. It can also be caused by a kill signal, sent by another thread, requesting the thread to stop execution. In both case, the host kernel K is in charge of the destruction. The scenario is more complex if the finishing thread T is running in ATTACH mode, because the parent thread TP must be informed of the completion of thread T, in case of pthread_join() executed by TP. |
| | 126 | The destruction of a thread T running in cluster K can be caused by the thread itself, executing the thread_exit() function. It can also be caused by another thread, executing the thread_kill() requesting the target thread to stop execution. In both case, the host kernel K is in charge of the destruction. The scenario is more complex if the finishing thread T is running in DETACHED mode, because the parent thread TP must be informed of the completion of thread T, in case of pthread_join() executed by TP. |
| 130 | | It T is running in ATTACH mode, the host cluster K force the T state to ZOMBI, to prevent the thread to be scheduled. If the thread completion is caused by an exit, the thread T stops immediately execution. If it is caused by a kill signal, the signal is registered in the thread descriptor, and the rescheduling will only occur at the next scheduling point. |
| 131 | | If T is not running in attached mode, the scenario is similar, but the T is directly forced to the DEAD state. |
| | 130 | * If T is running in DETACHED mode, the calling thread T sets the FLAG_SUICIDE bit in the "flags" bit_vector, registers the BLOCKED_GLOBAL bit in the "blocked" bit_vector, and de-schedule. The scheduler, detecting the FLAG_SUICIDE bit, remove the thread from the scheduler list, remove the thread from its process, and destroys the thread descriptor. |
| | 131 | * If it is running in ATTACHED mode, the calling thread T sets the BLOCKED_EXIT bit in the "blocked" bit vector and de-schedule. The FLAG_KILL bit in the "flags" bit-vector, and the BLOCKED_EXIT bit are set by the parent thread TP (using remote accesses) when it executes the pthread_join(), and detects the BLOCKED_EXIT bit in thread T. The scenario is the standard kill described below. |
| 135 | | This second phase is only required, in the parent thread cluster M, if T is running in ATTACH mode. The parent thread descriptor maintains a global list of all children threads running in ATTACH mode. When the parent thread execute the pthread_join() system call for a child identified by its TRDID, the M kernel scan this list to localize the selected child thread, and directly poll the child thread status using a remote_read access. When the M kernel detects the completion of T (ZOMBI state), it send a RPC_THREAD_USER_JOIN to the K cluster containing the T thread to ask the K kernel to change the state of T from ZOMBI to DEAD. |
| | 135 | This is a three steps scenario: |
| | 136 | |
| | 137 | 1. The killer thread uses a remote access to set the BLOCKED_GLOBAL bit in the target thread "blocked" bit_vector, set the FLAG_KILL bit in the target thread "signals" bit_vector, and send an IPI to the target thread core to force scheduling. |
| | 138 | 1. The target thread scheduler, detecting the FLAG_KILL bit set, removes the thread from the scheduler list, and reset the FLAG_KILL bit to acknowledge the killer. |
| | 139 | 1. The killer thread poll the FLAG_KILL bit in the target thread until reset, detach the thread from its parent if the thread is attached, and destroys the target thread, using a RPC_THREAD_DESTROY if the target thread is remote. |
| | 140 | |
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