pthread_rwlockattr_setkind_np, pthread_rwlockattr_getkind_np — set/get the read-write lock kind of the thread read-write lock attribute object
||const pthread_rwlockattr_t *attr,|
Compile and link with
sets the "lock kind" attribute of the read-write lock
attribute object referred to by
attr to the value specified in
pref. The argument
pref may be set to
one of the following:
This is the default. A thread may hold multiple read
locks; that is, read locks are recursive. According to
The Single Unix Specification, the behavior is
unspecified when a reader tries to place a lock, and
there is no write lock but writers are waiting. Giving
preference to the reader, as is set by
implies that the reader will receive the requested
lock, even if a writer is waiting. As long as there are
readers, the writer will be starved.
This is intended as the write lock analog of
Setting the lock kind to this avoids writer starvation as long as any read locking is not done in a recursive fashion.
returns the value of the lock kind attribute of the
read-write lock attribute object referred to by
attr in the pointer
On success, these functions return 0. Given valid pointer
succeeds. On error,
pthread_rwlockattr_setkind_np() returns a
non-zero error number.
Setting the value read-write lock kind to
PTHREAD_RWLOCK_PREFER_WRITER_NP results in
the same behavior as setting the value to
PTHREAD_RWLOCK_PREFER_READER_NP. As long as
a reader thread holds the lock, the thread holding a write
lock will be starved. Setting the lock kind to
allows writers to run, but, as the name implies a writer may
not lock recursively.
functions first appeared in glibc 2.1.
These functions are non-standard GNU extensions; hence the suffix "_np" (non-portable) in the names.
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