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| author | Alejandro Colomar <alx@kernel.org> | 2023-03-17 17:08:01 +0100 |
|---|---|---|
| committer | Alejandro Colomar <alx@kernel.org> | 2023-03-30 15:14:55 +0200 |
| commit | 4131356cdab8d37fc395ca5466a0401c8573380c (patch) | |
| tree | 8c4c6f1c3172358b735b481cbbfdd9cc04b00ed9 /man2/timer_create.2 | |
| parent | fd00f831b52d61a91d59cb3b46182869145d9700 (diff) | |
| download | man-pages-4131356cdab8.tar.gz | |
man*/, man-pages.7: VERSIONS, STANDARDS, HISTORY: Reorganize sections
- Add a new HISTORY section that covers the history of an API, both
regarding implementations and regarding old standards. This was
previously covered in VERSIONS, and in some cases in STANDARDS.
- Repurpose VERSIONS to cover differing implementations in _current_
systems.
- STANDARDS is reduced to only cover current versions of standards.
That basically means only C11 (C99 has been superseeded by C11; C17
is just a bugfix of C11, so not really a new version), and
POSIX.1-2008 (*-2001 was superseeded by *-2008; *-2017 was just a
bugfix for *-2008). The section also mentions for example 'Linux',
'GNU' or 'BSD' when a non-standard API is Linux- or GNU-only or if
it's (de-facto) standard in the BSDs.
- In some cases content that should go into one of these sections was
in NOTES. Move it from there to where it corresponds.
- In the SYNOPSIS, I added [[deprecated]] in some functions that I
found are deprecated by the relevant standards.
- A few other related changes...
Cc: Oskari Pirhonen <xxc3ncoredxx@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Diffstat (limited to 'man2/timer_create.2')
| -rw-r--r-- | man2/timer_create.2 | 88 |
1 files changed, 44 insertions, 44 deletions
diff --git a/man2/timer_create.2 b/man2/timer_create.2 index 6d49da17f8..ba5ad78fb3 100644 --- a/man2/timer_create.2 +++ b/man2/timer_create.2 @@ -222,9 +222,51 @@ but the caller did not have the .B CAP_WAKE_ALARM capability. .SH VERSIONS -This system call is available since Linux 2.6. +.SS C library/kernel differences +Part of the implementation of the POSIX timers API is provided by glibc. +.\" See nptl/sysdeps/unix/sysv/linux/timer_create.c +In particular: +.IP \[bu] 3 +Much of the functionality for +.B SIGEV_THREAD +is implemented within glibc, rather than the kernel. +(This is necessarily so, +since the thread involved in handling the notification is one +that must be managed by the C library POSIX threads implementation.) +Although the notification delivered to the process is via a thread, +internally the NPTL implementation uses a +.I sigev_notify +value of +.B SIGEV_THREAD_ID +along with a real-time signal that is reserved by the implementation (see +.BR nptl (7)). +.IP \[bu] +The implementation of the default case where +.I evp +is NULL is handled inside glibc, +which invokes the underlying system call with a suitably populated +.I sigevent +structure. +.IP \[bu] +The timer IDs presented at user level are maintained by glibc, +which maps these IDs to the timer IDs employed by the kernel. +.\" See the glibc source file kernel-posix-timers.h for the structure +.\" that glibc uses to map user-space timer IDs to kernel timer IDs +.\" The kernel-level timer ID is exposed via siginfo.si_tid. .SH STANDARDS -POSIX.1-2001, POSIX.1-2008. +POSIX.1-2008. +.SH HISTORY +Linux 2.6. +POSIX.1-2001. +.PP +Prior to Linux 2.6, +glibc provided an incomplete user-space implementation +.RB ( CLOCK_REALTIME +timers only) using POSIX threads, +and before glibc 2.17, +.\" glibc commit 93a78ac437ba44f493333d7e2a4b0249839ce460 +the implementation falls back to this technique on systems +running kernels older than Linux 2.6. .SH NOTES A program may create multiple interval timers using .BR timer_create (). @@ -277,48 +319,6 @@ support for POSIX timers is a configurable option that is enabled by default. Kernel support can be disabled via the .B CONFIG_POSIX_TIMERS option. -.\" -.SS C library/kernel differences -Part of the implementation of the POSIX timers API is provided by glibc. -.\" See nptl/sysdeps/unix/sysv/linux/timer_create.c -In particular: -.IP \[bu] 3 -Much of the functionality for -.B SIGEV_THREAD -is implemented within glibc, rather than the kernel. -(This is necessarily so, -since the thread involved in handling the notification is one -that must be managed by the C library POSIX threads implementation.) -Although the notification delivered to the process is via a thread, -internally the NPTL implementation uses a -.I sigev_notify -value of -.B SIGEV_THREAD_ID -along with a real-time signal that is reserved by the implementation (see -.BR nptl (7)). -.IP \[bu] -The implementation of the default case where -.I evp -is NULL is handled inside glibc, -which invokes the underlying system call with a suitably populated -.I sigevent -structure. -.IP \[bu] -The timer IDs presented at user level are maintained by glibc, -which maps these IDs to the timer IDs employed by the kernel. -.\" See the glibc source file kernel-posix-timers.h for the structure -.\" that glibc uses to map user-space timer IDs to kernel timer IDs -.\" The kernel-level timer ID is exposed via siginfo.si_tid. -.PP -The POSIX timers system calls first appeared in Linux 2.6. -Prior to this, -glibc provided an incomplete user-space implementation -.RB ( CLOCK_REALTIME -timers only) using POSIX threads, -and before glibc 2.17, -.\" glibc commit 93a78ac437ba44f493333d7e2a4b0249839ce460 -the implementation falls back to this technique on systems -running kernels older than Linux 2.6. .SH EXAMPLES The program below takes two arguments: a sleep period in seconds, and a timer frequency in nanoseconds. |