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Diffstat (limited to 'lib/libc/sys/read.2')
| -rw-r--r-- | lib/libc/sys/read.2 | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/lib/libc/sys/read.2 b/lib/libc/sys/read.2 index b94341a..ea428fd 100644 --- a/lib/libc/sys/read.2 +++ b/lib/libc/sys/read.2 @@ -107,6 +107,53 @@ The system guarantees to read the number of bytes requested if the descriptor references a normal file that has that many bytes left before the end-of-file, but in no other case. .Pp +.Sh IMPLEMENTATION NOTES +.Pp +In the non-threaded library +.Fn read +is implemented as the +.Va read +syscall. +.Pp +In the threaded library, the +.Va read +syscall is assembled to +.Fn _thread_sys_read +and +.Fn read +is implemented as a function which locks +.Va d +for read, then calls +.Fn _thread_sys_read . +If the call to +.Fn _thread_sys_read +would block, a context switch is performed. Before returning, +.Fn read +unlocks +.Va d . +.Pp +In the non-threaded library +.Fn readv +is implemented as the +.Va readv +syscall. +.Pp +In the threaded library, the +.Va readv +syscall is assembled to +.Fn _thread_sys_readv +and +.Fn readv +is implemented as a function which locks +.Va d +for read, then calls +.Fn _thread_sys_readv . +If the call to +.Fn _thread_sys_readv +would block, a context switch is performed. Before returning, +.Fn readv +unlocks +.Va d . .Sh RETURN VALUES If successful, the number of bytes actually read is returned. Upon reading end-of-file, |
