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/*
* Copyright (c) 2014-2017 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <assert.h>
#include <stdalign.h>
#include <stddef.h>
#include <kern/atomic.h>
#include <kern/init.h>
#include <kern/macros.h>
#include <kern/percpu.h>
#include <kern/spinlock.h>
#include <kern/thread.h>
#include <kern/xcall.h>
#include <machine/cpu.h>
struct xcall {
alignas(CPU_L1_SIZE) xcall_fn_t fn;
void *arg;
};
/*
* Per-CPU data.
*
* Send calls are sent to remote processors. Their access is synchronized
* by disabling preemption.
*
* The received call points to either NULL if there is no call to process,
* or a remote send call otherwise. The lock serializes the complete
* inter-processor operation, i.e. setting the received call pointer,
* communication through an IPI, and waiting for the processor to
* acknowledge execution. By serializing interrupts, it is certain that
* there is a 1:1 mapping between interrupts and cross-calls, allowing
* the handler to process only one cross-call instead of iterating over
* a queue. This way, interrupts with higher priority can be handled
* between multiple cross-calls.
*/
struct xcall_cpu_data {
alignas(CPU_L1_SIZE) struct xcall send_calls[X15_MAX_CPUS];
struct xcall *recv_call;
struct spinlock lock;
};
static struct xcall_cpu_data xcall_cpu_data __percpu;
static inline void
xcall_set(struct xcall *call, xcall_fn_t fn, void *arg)
{
call->fn = fn;
call->arg = arg;
}
static void
xcall_cpu_data_init(struct xcall_cpu_data *cpu_data)
{
cpu_data->recv_call = NULL;
spinlock_init(&cpu_data->lock);
}
static struct xcall_cpu_data *
xcall_cpu_data_get(void)
{
assert(!thread_preempt_enabled());
return cpu_local_ptr(xcall_cpu_data);
}
static struct xcall *
xcall_cpu_data_get_send_call(struct xcall_cpu_data *cpu_data, unsigned int cpu)
{
assert(cpu < ARRAY_SIZE(cpu_data->send_calls));
return &cpu_data->send_calls[cpu];
}
static struct xcall *
xcall_cpu_data_get_recv_call(const struct xcall_cpu_data *cpu_data)
{
return atomic_load(&cpu_data->recv_call, ATOMIC_ACQUIRE);
}
static void
xcall_cpu_data_set_recv_call(struct xcall_cpu_data *cpu_data,
struct xcall *call)
{
atomic_store(&cpu_data->recv_call, call, ATOMIC_RELEASE);
}
static void
xcall_cpu_data_clear_recv_call(struct xcall_cpu_data *cpu_data)
{
xcall_cpu_data_set_recv_call(cpu_data, NULL);
}
static int __init
xcall_setup(void)
{
unsigned int i;
for (i = 0; i < cpu_count(); i++) {
xcall_cpu_data_init(percpu_ptr(xcall_cpu_data, i));
}
return 0;
}
INIT_OP_DEFINE(xcall_setup,
INIT_OP_DEP(thread_bootstrap, true),
INIT_OP_DEP(spinlock_setup, true));
void
xcall_call(xcall_fn_t fn, void *arg, unsigned int cpu)
{
struct xcall_cpu_data *local_data, *remote_data;
struct xcall *call;
assert(cpu_intr_enabled());
assert(fn != NULL);
remote_data = percpu_ptr(xcall_cpu_data, cpu);
thread_preempt_disable();
local_data = xcall_cpu_data_get();
call = xcall_cpu_data_get_send_call(local_data, cpu);
xcall_set(call, fn, arg);
spinlock_lock(&remote_data->lock);
xcall_cpu_data_set_recv_call(remote_data, call);
cpu_send_xcall(cpu);
while (xcall_cpu_data_get_recv_call(remote_data) != NULL) {
cpu_pause();
}
spinlock_unlock(&remote_data->lock);
thread_preempt_enable();
}
void
xcall_intr(void)
{
struct xcall_cpu_data *cpu_data;
struct xcall *call;
assert(thread_check_intr_context());
cpu_data = xcall_cpu_data_get();
call = xcall_cpu_data_get_recv_call(cpu_data);
call->fn(call->arg);
xcall_cpu_data_clear_recv_call(cpu_data);
}
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