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bpf: make timer data struct more generic

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To be able to add workqueues and reuse most of the timer code, we need
to make bpf_hrtimer more generic.

There is no code change except that the new struct gets a new u64 flags
attribute. We are still below 2 cache lines, so this shouldn't impact
the current running codes.

The ordering is also changed. Everything related to async callback
is now on top of bpf_hrtimer.

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/20240420-bpf_wq-v2-1-6c986a5a741f@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Benjamin Tissoires 2024-04-20 11:09:01 +02:00 committed by Alexei Starovoitov
parent a7de265cb2
commit be2749beff
1 changed files with 38 additions and 33 deletions
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71
kernel/bpf/helpers.c
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@ -1079,11 +1079,20 @@ const struct bpf_func_proto bpf_snprintf_proto = {
.arg5_type = ARG_CONST_SIZE_OR_ZERO,
};
struct bpf_async_cb {
struct bpf_map *map;
struct bpf_prog *prog;
void __rcu *callback_fn;
void *value;
struct rcu_head rcu;
u64 flags;
};
/* BPF map elements can contain 'struct bpf_timer'.
* Such map owns all of its BPF timers.
* 'struct bpf_timer' is allocated as part of map element allocation
* and it's zero initialized.
* That space is used to keep 'struct bpf_timer_kern'.
* That space is used to keep 'struct bpf_async_kern'.
* bpf_timer_init() allocates 'struct bpf_hrtimer', inits hrtimer, and
* remembers 'struct bpf_map *' pointer it's part of.
* bpf_timer_set_callback() increments prog refcnt and assign bpf callback_fn.
@ -1096,16 +1105,12 @@ const struct bpf_func_proto bpf_snprintf_proto = {
* freeing the timers when inner map is replaced or deleted by user space.
*/
struct bpf_hrtimer {
struct bpf_async_cb cb;
struct hrtimer timer;
struct bpf_map *map;
struct bpf_prog *prog;
void __rcu *callback_fn;
void *value;
struct rcu_head rcu;
};
/* the actual struct hidden inside uapi struct bpf_timer */
struct bpf_timer_kern {
struct bpf_async_kern {
struct bpf_hrtimer *timer;
/* bpf_spin_lock is used here instead of spinlock_t to make
* sure that it always fits into space reserved by struct bpf_timer
@ -1119,14 +1124,14 @@ static DEFINE_PER_CPU(struct bpf_hrtimer *, hrtimer_running);
static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer)
{
struct bpf_hrtimer *t = container_of(hrtimer, struct bpf_hrtimer, timer);
struct bpf_map *map = t->map;
void *value = t->value;
struct bpf_map *map = t->cb.map;
void *value = t->cb.value;
bpf_callback_t callback_fn;
void *key;
u32 idx;
BTF_TYPE_EMIT(struct bpf_timer);
callback_fn = rcu_dereference_check(t->callback_fn, rcu_read_lock_bh_held());
callback_fn = rcu_dereference_check(t->cb.callback_fn, rcu_read_lock_bh_held());
if (!callback_fn)
goto out;
@ -1155,7 +1160,7 @@ out:
return HRTIMER_NORESTART;
}
BPF_CALL_3(bpf_timer_init, struct bpf_timer_kern *, timer, struct bpf_map *, map,
BPF_CALL_3(bpf_timer_init, struct bpf_async_kern *, timer, struct bpf_map *, map,
u64, flags)
{
clockid_t clockid = flags & (MAX_CLOCKS - 1);
@ -1163,8 +1168,8 @@ BPF_CALL_3(bpf_timer_init, struct bpf_timer_kern *, timer, struct bpf_map *, map
int ret = 0;
BUILD_BUG_ON(MAX_CLOCKS != 16);
BUILD_BUG_ON(sizeof(struct bpf_timer_kern) > sizeof(struct bpf_timer));
BUILD_BUG_ON(__alignof__(struct bpf_timer_kern) != __alignof__(struct bpf_timer));
BUILD_BUG_ON(sizeof(struct bpf_async_kern) > sizeof(struct bpf_timer));
BUILD_BUG_ON(__alignof__(struct bpf_async_kern) != __alignof__(struct bpf_timer));
if (in_nmi())
return -EOPNOTSUPP;
@ -1187,10 +1192,10 @@ BPF_CALL_3(bpf_timer_init, struct bpf_timer_kern *, timer, struct bpf_map *, map
ret = -ENOMEM;
goto out;
}
t->value = (void *)timer - map->record->timer_off;
t->map = map;
t->prog = NULL;
rcu_assign_pointer(t->callback_fn, NULL);
t->cb.value = (void *)timer - map->record->timer_off;
t->cb.map = map;
t->cb.prog = NULL;
rcu_assign_pointer(t->cb.callback_fn, NULL);
hrtimer_init(&t->timer, clockid, HRTIMER_MODE_REL_SOFT);
t->timer.function = bpf_timer_cb;
WRITE_ONCE(timer->timer, t);
@ -1222,7 +1227,7 @@ static const struct bpf_func_proto bpf_timer_init_proto = {
.arg3_type = ARG_ANYTHING,
};
BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callback_fn,
BPF_CALL_3(bpf_timer_set_callback, struct bpf_async_kern *, timer, void *, callback_fn,
struct bpf_prog_aux *, aux)
{
struct bpf_prog *prev, *prog = aux->prog;
@ -1237,7 +1242,7 @@ BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callb
ret = -EINVAL;
goto out;
}
if (!atomic64_read(&t->map->usercnt)) {
if (!atomic64_read(&t->cb.map->usercnt)) {
/* maps with timers must be either held by user space
* or pinned in bpffs. Otherwise timer might still be
* running even when bpf prog is detached and user space
@ -1246,7 +1251,7 @@ BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callb
ret = -EPERM;
goto out;
}
prev = t->prog;
prev = t->cb.prog;
if (prev != prog) {
/* Bump prog refcnt once. Every bpf_timer_set_callback()
* can pick different callback_fn-s within the same prog.
@ -1259,9 +1264,9 @@ BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callb
if (prev)
/* Drop prev prog refcnt when swapping with new prog */
bpf_prog_put(prev);
t->prog = prog;
t->cb.prog = prog;
}
rcu_assign_pointer(t->callback_fn, callback_fn);
rcu_assign_pointer(t->cb.callback_fn, callback_fn);
out:
__bpf_spin_unlock_irqrestore(&timer->lock);
return ret;
@ -1275,7 +1280,7 @@ static const struct bpf_func_proto bpf_timer_set_callback_proto = {
.arg2_type = ARG_PTR_TO_FUNC,
};
BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, flags)
BPF_CALL_3(bpf_timer_start, struct bpf_async_kern *, timer, u64, nsecs, u64, flags)
{
struct bpf_hrtimer *t;
int ret = 0;
@ -1287,7 +1292,7 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla
return -EINVAL;
__bpf_spin_lock_irqsave(&timer->lock);
t = timer->timer;
if (!t || !t->prog) {
if (!t || !t->cb.prog) {
ret = -EINVAL;
goto out;
}
@ -1315,18 +1320,18 @@ static const struct bpf_func_proto bpf_timer_start_proto = {
.arg3_type = ARG_ANYTHING,
};
static void drop_prog_refcnt(struct bpf_hrtimer *t)
static void drop_prog_refcnt(struct bpf_async_cb *async)
{
struct bpf_prog *prog = t->prog;
struct bpf_prog *prog = async->prog;
if (prog) {
bpf_prog_put(prog);
t->prog = NULL;
rcu_assign_pointer(t->callback_fn, NULL);
async->prog = NULL;
rcu_assign_pointer(async->callback_fn, NULL);
}
}
BPF_CALL_1(bpf_timer_cancel, struct bpf_timer_kern *, timer)
BPF_CALL_1(bpf_timer_cancel, struct bpf_async_kern *, timer)
{
struct bpf_hrtimer *t;
int ret = 0;
@ -1348,7 +1353,7 @@ BPF_CALL_1(bpf_timer_cancel, struct bpf_timer_kern *, timer)
ret = -EDEADLK;
goto out;
}
drop_prog_refcnt(t);
drop_prog_refcnt(&t->cb);
out:
__bpf_spin_unlock_irqrestore(&timer->lock);
/* Cancel the timer and wait for associated callback to finish
@ -1371,7 +1376,7 @@ static const struct bpf_func_proto bpf_timer_cancel_proto = {
*/
void bpf_timer_cancel_and_free(void *val)
{
struct bpf_timer_kern *timer = val;
struct bpf_async_kern *timer = val;
struct bpf_hrtimer *t;
/* Performance optimization: read timer->timer without lock first. */
@ -1383,7 +1388,7 @@ void bpf_timer_cancel_and_free(void *val)
t = timer->timer;
if (!t)
goto out;
drop_prog_refcnt(t);
drop_prog_refcnt(&t->cb);
/* The subsequent bpf_timer_start/cancel() helpers won't be able to use
* this timer, since it won't be initialized.
*/
@ -1410,7 +1415,7 @@ out:
*/
if (this_cpu_read(hrtimer_running) != t)
hrtimer_cancel(&t->timer);
kfree_rcu(t, rcu);
kfree_rcu(t, cb.rcu);
}
BPF_CALL_2(bpf_kptr_xchg, void *, map_value, void *, ptr)