/*
* For each partition that XPC has established communications with, there is
* a minimum of one kernel thread assigned to perform any operation that
* may potentially sleep or block (basically the callouts to the asynchronous
* functions registered via xpc_connect()).
*
* Additional kthreads are created and destroyed by XPC as the workload
* demands.
*
* A kthread is assigned to one of the active channels that exists for a given
* partition.
*/
void
xpc_create_kthreads(struct xpc_channel *ch, int needed,
int ignore_disconnecting)
{
unsigned long irq_flags;
u64 args = XPC_PACK_ARGS(ch->partid, ch->number);
struct xpc_partition *part = &xpc_partitions[ch->partid];
struct task_struct *kthread;
while (needed-- > 0) {
/*
* The following is done on behalf of the newly created
* kthread. That kthread is responsible for doing the
* counterpart to the following before it exits.
*/
if (ignore_disconnecting) {
if (!atomic_inc_not_zero(&ch->kthreads_assigned)) {
/* kthreads assigned had gone to zero */
BUG_ON(!(ch->flags &
XPC_C_DISCONNECTINGCALLOUT_MADE));
break;
}
} else if (ch->flags & XPC_C_DISCONNECTING) {
break;
} else if (atomic_inc_return(&ch->kthreads_assigned) == 1 &&
atomic_inc_return(&part->nchannels_engaged) == 1) {
xpc_indicate_partition_engaged(part);
}
(void)xpc_part_ref(part);
xpc_msgqueue_ref(ch);
kthread = kthread_run(xpc_kthread_start, (void *)args,
"xpc%02dc%d", ch->partid, ch->number);
if (IS_ERR(kthread)) {
/* the fork failed */
/*
* NOTE: if (ignore_disconnecting &&
* !(ch->flags & XPC_C_DISCONNECTINGCALLOUT)) is true,
* then we'll deadlock if all other kthreads assigned
* to this channel are blocked in the channel's
* registerer, because the only thing that will unblock
* them is the xpDisconnecting callout that this
* failed kthread_run() would have made.
*/
if (atomic_dec_return(&ch->kthreads_assigned) == 0 &&
atomic_dec_return(&part->nchannels_engaged) == 0) {
xpc_indicate_partition_disengaged(part);
}
xpc_msgqueue_deref(ch);
xpc_part_deref(part);
if (atomic_read(&ch->kthreads_assigned) <
ch->kthreads_idle_limit) {
/*
* Flag this as an error only if we have an
* insufficient #of kthreads for the channel
* to function.
*/
spin_lock_irqsave(&ch->lock, irq_flags);
XPC_DISCONNECT_CHANNEL(ch, xpLackOfResources,
&irq_flags);
spin_unlock_irqrestore(&ch->lock, irq_flags);
}
break;
}
}
}
void
xpc_create_kthreads(struct xpc_channel *ch, int needed,
int ignore_disconnecting)
{
unsigned long irq_flags;
u64 args = XPC_PACK_ARGS(ch->partid, ch->number);
struct xpc_partition *part = &xpc_partitions[ch->partid];
struct task_struct *kthread;
void (*indicate_partition_disengaged) (struct xpc_partition *) =
xpc_arch_ops.indicate_partition_disengaged;
while (needed-- > 0) {
/*
*/
if (ignore_disconnecting) {
if (!atomic_inc_not_zero(&ch->kthreads_assigned)) {
/* */
BUG_ON(!(ch->flags &
XPC_C_DISCONNECTINGCALLOUT_MADE));
break;
}
} else if (ch->flags & XPC_C_DISCONNECTING) {
break;
} else if (atomic_inc_return(&ch->kthreads_assigned) == 1 &&
atomic_inc_return(&part->nchannels_engaged) == 1) {
xpc_arch_ops.indicate_partition_engaged(part);
}
(void)xpc_part_ref(part);
xpc_msgqueue_ref(ch);
kthread = kthread_run(xpc_kthread_start, (void *)args,
"xpc%02dc%d", ch->partid, ch->number);
if (IS_ERR(kthread)) {
/* */
/*
*/
if (atomic_dec_return(&ch->kthreads_assigned) == 0 &&
atomic_dec_return(&part->nchannels_engaged) == 0) {
indicate_partition_disengaged(part);
}
xpc_msgqueue_deref(ch);
xpc_part_deref(part);
if (atomic_read(&ch->kthreads_assigned) <
ch->kthreads_idle_limit) {
/*
*/
spin_lock_irqsave(&ch->lock, irq_flags);
XPC_DISCONNECT_CHANNEL(ch, xpLackOfResources,
&irq_flags);
spin_unlock_irqrestore(&ch->lock, irq_flags);
}
break;
}
}
}
