Changes between Version 57 and Version 58 of processus_thread


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Timestamp:
Dec 8, 2017, 1:40:06 AM (4 years ago)
Author:
alain
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  • processus_thread

    v57 v58  
    8989 * the '''thread pointer''' register contains the current thread descriptor address. This '''thread pointer''' register cannot have the same value for parent and child.   
    9090 * the '''stack pointer''' register contains the current pointer on the kernel stack. ALMOS-MKH uses a specific kernel stack when an user thread enters the kernel, and this kernel stack is implemented in the thread descriptor. As parent and child cannot use the same kernel stack, the parent kernel stack content is copied to the child kernel stack, and the '''stack pointer''' register cannot have the same value for parent and child.
    91  * the '''page table pointer''' register contains the physical base address of the current generic page table. As the child GPT is a copy of the parent GPT in the child cluster, this '''page table
    92 register''' cannot have the same value for parent and child.
     91 * the '''page table pointer''' register contains the physical base address of the current generic page table. As the child GPT is a copy of the parent GPT in the child cluster, this '''page table register''' cannot have the same value for parent and child.
    9392
    9493At the end of the fork(), cluster Y is both the owner cluster and the reference cluster for the new  C process, that contains one single thread running in the Y cluster.
     
    9796=== 3.2) exec() ===
    9897
    99 After a fork() system call, any thread of the the P process can execute an exec() system call. This system call forces the P process to execute a new application, while keeping the same PID,
    100 the same parent process, all open file descriptors, and the environment variables. The existing P process descriptors (both the reference and the copies)  and all associated threads are destroyed. A new process descriptor and a new main thread descriptor are created in the reference cluster, and initialized from values found in the existing process descriptor, and from values contained in the .elf file defining the new application. The calling thread  can run in any cluster. If the reference cluster Z for process P is different from the calling thread cluster X, the calling thread must use a RPC to ask the reference cluster Z to do the work.
     98After a fork() system call, any thread of the the P process can execute an exec() system call. This system call forces the P process to execute a new application, while keeping the same PID, the same parent process, all open file descriptors, and the environment variables. The existing P process descriptors (both the reference and the copies)  and all associated threads will be destroyed. A new process descriptor and a new main thread descriptor are created in the reference cluster, and initialized from values found in the existing process descriptor, and from values contained in the .elf file defining the new application. The calling thread  can run in any cluster. If the reference cluster Z for process P is different from the calling thread cluster X, the calling thread must use a RPC to ask the reference cluster Z to do the work.
    10199
    102100At the end of the exec() system call, the cluster Z is both the owner and the reference cluster for process C, that contains one single thread in cluster Z.
     
    104102== __4) Thread creation__ ==
    105103
    106 Any thread T of any process P, running in any cluster K, can create a new thread NT in any cluster M. This creation is driven by the ''pthread_create'' system call. The target M cluster is called the host cluster. If the M cluster does not contain a process descriptor copy for process P (because the NT thread is the first thread of process P in cluster M), a new process descriptor must be created in cluster M.
     104Any thread T of any process P, running in any cluster K, can create a new thread NT in any cluster M. This creation is initiated by the ''pthread_create'' system call. The target M cluster is called the host cluster.
    107105 * The target cluster M can be specified by the user application, using the CXY field of the pthread_attr_t argument. If the CXY is not defined by the user, the target cluster M is selected by the kernel K, using the DQDT.
    108  * The Target core in cluster M can be specified by the user application, using the CORE_LID field of the pthread_attr_t argument. If the CORE_LID is not defined by the user, the target core is selected by the target kernel M.
     106 * The target core in cluster M can be specified by the user application, using the CORE_LID field of the pthread_attr_t argument. If the CORE_LID is not defined by the user, the target core is selected by the target kernel M.
    109107
    110 If the target cluster M is different from the client cluster, the cluster K send a RPC_THREAD_USER_CREATE request to cluster M. The argument is a complete structure pthread_attr_t (defined in the ''thread.h'' file in ALMOS-MK), containing the PID, the function to execute and its arguments, and optionally, the target cluster and target core. This RPC should return the thread TRDID. The detailed scenario is the following:
     108If the target cluster M is different from the client cluster, the cluster K send a RPC_THREAD_USER_CREATE request to cluster M. The argument is a complete structure pthread_attr_t (defined in the ''thread.h'' file in ALMOS-MK), containing the PID, the function to execute and its arguments, and optionally, the target cluster and target core. This RPC should return the thread TRDID.
    111109
    112  1. The kernel M checks if it contains a copy of the P process descriptor.
    113  1. If not, the kernel M creates a process descriptor copy from the reference P process descriptor, using a remote_memcpy(), and using the cluster_get_reference_process_from_pid() to get the extended pointer on reference cluster. It allocates memory for the associated structures GPT(M,P), VSL(M,P), FDT(M,P). It initializes (partially) these structures by using remote_memcpy() from the reference cluster. The PG_TBL structure will be filled by the page faults.
    114  1. The kernel M register this new process descriptor in the COPIES_LIST and LOCAL_LIST.
    115  1. When the local process descriptor is set, the kernel M select the core that will execute the thread, allocates a TRDID to this thread, and creates the thread descriptor for NT.
    116  1. The kernel M registers the thread descriptor in the local process descriptor  TH_TBL(M,P), and in the selected core scheduler.
    117  1. The kernel M returns the TRDID to the client cluster K, and acknowledge the RPC.
     110 * If the target cluster M does not contain a copy of the P process descriptor, the kernel M creates a process descriptor copy from the reference P process descriptor, using a remote_memcpy(), and using the cluster_get_reference_process_from_pid() to get the extended pointer on reference cluster. It allocates memory for the associated structures GPT(M,P), VSL(M,P), FDT(M,P).  These structures being used as read-only caches will be dynamically filled by the page faults. This new process descriptor is registered in the COPIES_LIST and in the LOCAL_LIST.
     111 * When the local process descriptor is set, the kernel M select the core that will execute the new thread, allocates a TRDID to this thread, creates the thread descritor, and registers it in the local process descriptor, and in the selected core scheduler.
     112
    118113
    119114== __5) Thread destruction__ ==