rw_write_held
Checks whether the specified reader-writer lock is held by a writer.
int rw_write_held(vmlinux`rwlock_t *rwlock) The rw_write_held function returns non zero if the specified
reader-writer lock (rwlock) is held by a writer. If the lock is held only
by readers or isn't held at all, rw_write_held returns zero.
Example 8-42 How to use rw_write_held to check whether a writer is holding a specified reader-writer lock
The example uses two clauses. The first clause triggers for when the
_raw_write_lock is entered, and uses rw_write_held
function to print whether a write lock is held. At this stage, no lock is held, so the
output returns 0. When the _raw_write_lock returns, a lock
is held and the rw_write_held function returns 1 and the
script exits.
fbt:vmlinux:_raw_write_lock:entry
{
self->wlock = (rwlock_t *)arg0;
printf("write entry %x\n", 0 != rw_write_held(self->wlock));
}
fbt:vmlinux:_raw_write_lock:return
/self->wlock/
{
printf("write return %x\n", 0 != rw_write_held(self->wlock));
exit(0)
}