.tsc_bits = LTTNG_COMPACT_TSC_BITS,
.alloc = RING_BUFFER_ALLOC_PER_CPU,
- .sync = RING_BUFFER_SYNC_GLOBAL,
+ .sync = RING_BUFFER_SYNC_PER_CPU,
.mode = RING_BUFFER_MODE_TEMPLATE,
.backend = RING_BUFFER_PAGE,
.output = RING_BUFFER_MMAP,
channel_destroy(chan->chan, chan->handle, 1);
}
+static
+bool refcount_get_saturate(long *ref)
+{
+ long old, _new, res;
+
+ old = uatomic_read(ref);
+ for (;;) {
+ if (old == LONG_MAX) {
+ return false; /* Saturated. */
+ }
+ _new = old + 1;
+ res = uatomic_cmpxchg(ref, old, _new);
+ if (res == old) {
+ if (_new == LONG_MAX) {
+ return false; /* Saturation. */
+ }
+ return true; /* Success. */
+ }
+ old = res;
+ }
+}
+
static
int lttng_event_reserve(struct lttng_ust_lib_ring_buffer_ctx *ctx,
uint32_t event_id)
struct lttng_channel *lttng_chan = channel_get_private(ctx->chan);
struct lttng_rseq_state rseq_state;
int ret, cpu;
+ bool put_fallback_ref = false;
if (lib_ring_buffer_begin(&client_config))
return -EPERM;
} else {
cpu = rseq_cpu_at_start(rseq_state);
}
+fallback:
ctx->cpu = cpu;
switch (lttng_chan->header_type) {
WARN_ON_ONCE(1);
}
+ if (caa_likely(ctx->ctx_len
+ >= sizeof(struct lttng_ust_lib_ring_buffer_ctx)))
+ ctx->rseq_state = rseq_state;
+
ret = lib_ring_buffer_reserve(&client_config, ctx);
- if (caa_unlikely(ret))
- goto put;
+ if (caa_unlikely(ret)) {
+ if (ret == -EAGAIN) {
+ assert(!put_fallback_ref);
+ put_fallback_ref = refcount_get_saturate(
+ <tng_chan->chan->u.reserve_fallback_ref);
+ cpu = lib_ring_buffer_get_cpu(&client_config);
+ if (caa_unlikely(cpu < 0)) {
+ ret = -EPERM;
+ goto end;
+ }
+ goto fallback;
+ }
+ goto end;
+ }
if (caa_likely(ctx->ctx_len
>= sizeof(struct lttng_ust_lib_ring_buffer_ctx))) {
if (lib_ring_buffer_backend_get_pages(&client_config, ctx,
}
lttng_write_event_header(&client_config, ctx, event_id);
- if (caa_likely(ctx->ctx_len
- >= sizeof(struct lttng_ust_lib_ring_buffer_ctx)))
- ctx->rseq_state = rseq_state;
+ if (caa_unlikely(put_fallback_ref))
+ uatomic_dec(<tng_chan->chan->u.reserve_fallback_ref);
return 0;
end:
lib_ring_buffer_end(&client_config);
+ if (put_fallback_ref)
+ uatomic_dec(<tng_chan->chan->u.reserve_fallback_ref);
return ret;
}