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| -rw-r--r-- | ChangeLog | 10 | ||||
| -rw-r--r-- | manual/process.texi | 60 | ||||
| -rw-r--r-- | manual/signal.texi | 4 |
3 files changed, 56 insertions, 18 deletions
@@ -1,3 +1,13 @@ +2018-12-14 Florian Weimer <fweimer@redhat.com> + + * manual/process.texi (Process Creation Concepts): Remove + documentation of process (ID) lifetime. List more process + creation functions. Reference Process Identification section. + (Process Identification): Add information about process ID + lifetime. Describe Linux thread/task IDs. + * manual/signal.texi (Signaling Another Process): Mention that the + signal is always sent to the process. + 2018-12-14 Gabriel F. T. Gomes <gabriel@inconstante.eti.br> * misc/Makefile (tests): Remove tst-efgcvt. Add tst-dbl-efgcvt diff --git a/manual/process.texi b/manual/process.texi index b82b91f9f1..652b0001b5 100644 --- a/manual/process.texi +++ b/manual/process.texi @@ -132,22 +132,19 @@ output channels of the command being executed. This section gives an overview of processes and of the steps involved in creating a process and making it run another program. -@cindex process ID -@cindex process lifetime -Each process is named by a @dfn{process ID} number. A unique process ID -is allocated to each process when it is created. The @dfn{lifetime} of -a process ends when its termination is reported to its parent process; -at that time, all of the process resources, including its process ID, -are freed. - @cindex creating a process @cindex forking a process @cindex child process @cindex parent process -Processes are created with the @code{fork} system call (so the operation -of creating a new process is sometimes called @dfn{forking} a process). -The @dfn{child process} created by @code{fork} is a copy of the original -@dfn{parent process}, except that it has its own process ID. +@cindex subprocess +A new processes is created when one of the functions +@code{posix_spawn}, @code{fork}, or @code{vfork} is called. (The +@code{system} and @code{popen} also create new processes internally.) +Due to the name of the @code{fork} function, the act of creating a new +process is sometimes called @dfn{forking} a process. Each new process +(the @dfn{child process} or @dfn{subprocess}) is allocated a process +ID, distinct from the process ID of the parent process. @xref{Process +Identification}. After forking a child process, both the parent and child processes continue to execute normally. If you want your program to wait for a @@ -174,11 +171,40 @@ too, instead of returning to the previous process image. @node Process Identification @section Process Identification -The @code{pid_t} data type represents process IDs. You can get the -process ID of a process by calling @code{getpid}. The function -@code{getppid} returns the process ID of the parent of the current -process (this is also known as the @dfn{parent process ID}). Your -program should include the header files @file{unistd.h} and +@cindex process ID +Each process is named by a @dfn{process ID} number, a value of type +@code{pid_t}. A process ID is allocated to each process when it is +created. Process IDs are reused over time. The lifetime of a process +ends when the parent process of the corresponding process waits on the +process ID after the process has terminated. @xref{Process +Completion}. (The parent process can arrange for such waiting to +happen implicitly.) A process ID uniquely identifies a process only +during the lifetime of the process. As a rule of thumb, this means +that the process must still be running. + +Process IDs can also denote process groups and sessions. +@xref{Job Control}. + +@cindex thread ID +@cindex task ID +@cindex thread group +On Linux, threads created by @code{pthread_create} also receive a +@dfn{thread ID}. The thread ID of the initial (main) thread is the +same as the process ID of the entire process. Thread IDs for +subsequently created threads are distinct. They are allocated from +the same numbering space as process IDs. Process IDs and thread IDs +are sometimes also referred to collectively as @dfn{task IDs}. In +contrast to processes, threads are never waited for explicitly, so a +thread ID becomes eligible for reuse as soon as a thread exits or is +canceled. This is true even for joinable threads, not just detached +threads. Threads are assigned to a @dfn{thread group}. In +@theglibc{} implementation running on Linux, the process ID is the +thread group ID of all threads in the process. + +You can get the process ID of a process by calling @code{getpid}. The +function @code{getppid} returns the process ID of the parent of the +current process (this is also known as the @dfn{parent process ID}). +Your program should include the header files @file{unistd.h} and @file{sys/types.h} to use these functions. @pindex sys/types.h @pindex unistd.h diff --git a/manual/signal.texi b/manual/signal.texi index 9577ff091d..8b3a52e22a 100644 --- a/manual/signal.texi +++ b/manual/signal.texi @@ -2246,7 +2246,9 @@ signal: @table @code @item @var{pid} > 0 -The process whose identifier is @var{pid}. +The process whose identifier is @var{pid}. (On Linux, the signal is +sent to the entire process even if @var{pid} is a thread ID distinct +from the process ID.) @item @var{pid} == 0 All processes in the same process group as the sender. |