postwait(2)postwait(2)NAME
postwait: pw_getukid(), pw_wait(), pw_post(), pw_postv(), pw_getvmax()
- lightweight synchronization mechanism
SYNOPSISDESCRIPTION
Postwait is a fast, lightweight sleep/wakeup mechanism that can be used
for synchronization by cooperating kernel threads within a single
process or between separate processes.
A thread calls to block. It resumes execution when it is posted by
another thread, the call expires, or is signaled. If one or more posts
are already pending, returns immediately.
Threads using postwait are identified by their ukid. A thread
retrieves its ukid by calling It shares this ukid with anyone it
chooses by any means it considers appropriate (for example, shared mem‐
ory).
is called with a timeout ts. If ts is NULL, the thread will not time‐
out. It will remain blocked until posted or a signal wakes it up.
If ts points to a zero-valued timespec, will return immediately with a
value (and indicating whether or not it was posted.
If ts points to a timespec whose value is greater than zero, the thread
will block for that amount of time unless it is posted or interrupted
by a signal, in which case the timespec pointed to by ts is updated
with the remaining time. The return value and are set to indicate the
reason the call returned.
is used to post many threads with a single call. It posts to all
threads in the targets array. An value for each target is returned in
the errors array. (0 indicates success.) If the errors pointer is
zero, no target-specific errors are copied out.
There is a maximum number of threads that can be posted with a single
call. This value is returned by
Posts sent to a kernel thread that already has a post pending against
it are discarded.
RETURN VALUE
returns 0 if it succeeds, -1 otherwise.
returns 0 if posted, -1 otherwise.
returns 0 if the post succeeds, -1 otherwise.
returns 0 if every post succeeds, -1 otherwise.
returns the maximum number of kernel threads that can be posted with a
single call to
ERRORS
sets to one of the following values if it fails:
ukid points to an illegal address. The reliable
detection of this error is implementation depen‐
dent.
sets to one of the following values if it fails:
was called with a timeout of 0 but the caller has no post(s)
pending.
was called with a timeout that expired.
ts points to an illegal address. The reliable
detection of this error is implementation depen‐
dent.
was interrupted
by a signal.
The timespec pointed to by ts is invalid.
sets to one of the following values if it fails:
The ukid refers to a non-existent kernel thread.
sets to one of the following values if it fails:
targets points to an illegal address. The reliable
detection of this error is implementation depen‐
dent.
errors points to an illegal address. The reliable
detection of this error is implementation depen‐
dent.
count is less than 0.
count exceeds the maximum value (as returned by
A ukid refers to a non-existent kernel thread.
postwait(2)