d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Rearrange function descriptions in more logical order.

Browse Source 
Be less alarmist about the dangers of abusing wakeup_one().

Requested by: kris, imp
This commit is contained in:
Greg Lehey 2007-03-04 23:42:58 +00:00
parent d348f4d384
commit 759ace7eca
1 changed files with 30 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
share/man/man9/sleep.9
View File

@ -87,30 +87,6 @@ Due to the limited space of those programs to display arbitrary strings,
this message should not be longer than 6 characters.
.Pp
The
.Fn wakeup_one
function is used to make the first thread in the queue that is
sleeping on the parameter
.Fa chan
runnable.
This can prevent the system from becoming saturated
when a large number of threads are sleeping on the same address,
but only one of them can actually do any useful work when made
runnable.
.Pp
The
.Fn wakeup_one
function does not work reliably if unrelated threads are sleeping on the same
address.
In this case, if a wakeup for one group of threads is delivered to a member of
another group, that thread will ignore the wakeup, and the correct thread will
never be woken up.
It is the programmer's responsibility to choose a unique
.Fa chan
value.
In case of doubt, do not use
.Fn wakeup_one .
.Pp
The
.Fn msleep
function is the general sleep call.
It suspends the current thread until a wakeup is
@ -212,6 +188,36 @@ The thread can not be awakened early by signals or calls to
.Fn wakeup
or
.Fn wakeup_one .
.Pp
The
.Fn wakeup_one
function makes the first thread in the queue that is sleeping on the
parameter
.Fa chan
runnable.
This reduces the load when a large number of threads are sleeping on
the same address, but only one of them can actually do any useful work
when made runnable.
.Pp
Due to the way it works, the
.Fn wakeup_one
function requires that only related threads sleep on a specific
.Fa chan
address.
It is the programmer's responsibility to choose a unique
.Fa chan
value.
The older
.Fn wakeup
function did not require this, though it was never good practice to for threads to share a
.Fa chan
value.
When converting from
.Fn wakeup
to
.Fn wakeup_one ,
pay particular attention to ensure that no other threads wait on the same
.Fa chan .
.Sh RETURN VALUES
See above.
.Sh SEE ALSO