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This performs a non-consuming read of the trace buffer. Signed-off-by: Vincent Donnefort diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c index 49c4ae127533..a744bbf48e88 100644 --- a/kernel/trace/trace_remote.c +++ b/kernel/trace/trace_remote.c @@ -18,14 +18,25 @@ #define TRACEFS_MODE_WRITE 0640 #define TRACEFS_MODE_READ 0440 +enum tri_type { + TRI_CONSUMING, + TRI_NONCONSUMING, +}; + struct trace_remote_iterator { struct trace_remote *remote; struct trace_seq seq; struct delayed_work poll_work; unsigned long lost_events; u64 ts; + union { + struct ring_buffer_iter **rb_iters; + struct ring_buffer_iter *rb_iter; + }; int cpu; int evt_cpu; + loff_t pos; + enum tri_type type; }; struct trace_remote { @@ -36,6 +47,8 @@ struct trace_remote { unsigned long trace_buffer_size; struct ring_buffer_remote rb_remote; struct mutex lock; + struct rw_semaphore reader_lock; + struct rw_semaphore *pcpu_reader_locks; unsigned int nr_readers; unsigned int poll_ms; bool tracing_on; @@ -225,6 +238,20 @@ static int trace_remote_get(struct trace_remote *remote, int cpu) if (ret) return ret; + if (cpu != RING_BUFFER_ALL_CPUS && !remote->pcpu_reader_locks) { + int lock_cpu; + + remote->pcpu_reader_locks = kcalloc(nr_cpu_ids, sizeof(*remote->pcpu_reader_locks), + GFP_KERNEL); + if (!remote->pcpu_reader_locks) { + trace_remote_try_unload(remote); + return -ENOMEM; + } + + for_each_possible_cpu(lock_cpu) + init_rwsem(&remote->pcpu_reader_locks[lock_cpu]); + } + remote->nr_readers++; return 0; @@ -239,6 +266,9 @@ static void trace_remote_put(struct trace_remote *remote) if (remote->nr_readers) return; + kfree(remote->pcpu_reader_locks); + remote->pcpu_reader_locks = NULL; + trace_remote_try_unload(remote); } @@ -253,6 +283,48 @@ static void __poll_remote(struct work_struct *work) msecs_to_jiffies(iter->remote->poll_ms)); } +static int __alloc_ring_buffer_iter(struct trace_remote_iterator *iter, int cpu) +{ + bool once = false; + + if (cpu != RING_BUFFER_ALL_CPUS) { + iter->rb_iter = ring_buffer_read_start(iter->remote->trace_buffer, cpu, GFP_KERNEL); + + return iter->rb_iter ? 0 : -ENOMEM; + } + + iter->rb_iters = kcalloc(nr_cpu_ids, sizeof(*iter->rb_iters), GFP_KERNEL); + if (!iter->rb_iters) + return -ENOMEM; + + for_each_possible_cpu(cpu) { + iter->rb_iters[cpu] = ring_buffer_read_start(iter->remote->trace_buffer, cpu, + GFP_KERNEL); + if (iter->rb_iters[cpu]) + once = true; + } + + return once ? 0 : -ENOMEM; +} + +static void __free_ring_buffer_iter(struct trace_remote_iterator *iter, int cpu) +{ + if (!iter->rb_iter) + return; + + if (cpu != RING_BUFFER_ALL_CPUS) { + ring_buffer_read_finish(iter->rb_iter); + return; + } + + for_each_possible_cpu(cpu) { + if (iter->rb_iters[cpu]) + ring_buffer_read_finish(iter->rb_iters[cpu]); + } + + kfree(iter->rb_iters); +} + static struct trace_remote_iterator *trace_remote_iter(struct trace_remote *remote, int cpu, enum tri_type type) { @@ -261,6 +333,8 @@ static struct trace_remote_iterator lockdep_assert_held(&remote->lock); + if (type == TRI_NONCONSUMING && !trace_remote_loaded(remote)) + return NULL; ret = trace_remote_get(remote, cpu); if (ret) @@ -275,9 +349,21 @@ static struct trace_remote_iterator if (iter) { iter->remote = remote; iter->cpu = cpu; + iter->type = type; trace_seq_init(&iter->seq); - INIT_DELAYED_WORK(&iter->poll_work, __poll_remote); - schedule_delayed_work(&iter->poll_work, msecs_to_jiffies(remote->poll_ms)); + + switch (type) { + case TRI_CONSUMING: + INIT_DELAYED_WORK(&iter->poll_work, __poll_remote); + schedule_delayed_work(&iter->poll_work, msecs_to_jiffies(remote->poll_ms)); + break; + case TRI_NONCONSUMING: + ret = __alloc_ring_buffer_iter(iter, cpu); + break; + } + + if (ret) + goto err; return iter; } @@ -301,10 +387,100 @@ static void trace_remote_iter_free(struct trace_remote_iterator *iter) lockdep_assert_held(&remote->lock); + switch (iter->type) { + case TRI_CONSUMING: + cancel_delayed_work_sync(&iter->poll_work); + break; + case TRI_NONCONSUMING: + __free_ring_buffer_iter(iter, iter->cpu); + break; + } + kfree(iter); trace_remote_put(remote); } +static void trace_remote_iter_read_start(struct trace_remote_iterator *iter) +{ + struct trace_remote *remote = iter->remote; + int cpu = iter->cpu; + + /* Acquire global reader lock */ + if (cpu == RING_BUFFER_ALL_CPUS && iter->type == TRI_CONSUMING) + down_write(&remote->reader_lock); + else + down_read(&remote->reader_lock); + + if (cpu == RING_BUFFER_ALL_CPUS) + return; + + /* + * No need for the remote lock here, iter holds a reference on + * remote->nr_readers + */ + + /* Get the per-CPU one */ + if (WARN_ON_ONCE(!remote->pcpu_reader_locks)) + return; + + if (iter->type == TRI_CONSUMING) + down_write(&remote->pcpu_reader_locks[cpu]); + else + down_read(&remote->pcpu_reader_locks[cpu]); +} + +static void trace_remote_iter_read_finished(struct trace_remote_iterator *iter) +{ + struct trace_remote *remote = iter->remote; + int cpu = iter->cpu; + + /* Release per-CPU reader lock */ + if (cpu != RING_BUFFER_ALL_CPUS) { + /* + * No need for the remote lock here, iter holds a reference on + * remote->nr_readers + */ + if (iter->type == TRI_CONSUMING) + up_write(&remote->pcpu_reader_locks[cpu]); + else + up_read(&remote->pcpu_reader_locks[cpu]); + } + + /* Release global reader lock */ + if (cpu == RING_BUFFER_ALL_CPUS && iter->type == TRI_CONSUMING) + up_write(&remote->reader_lock); + else + up_read(&remote->reader_lock); +} + +static struct ring_buffer_iter *__get_rb_iter(struct trace_remote_iterator *iter, int cpu) +{ + return iter->cpu != RING_BUFFER_ALL_CPUS ? iter->rb_iter : iter->rb_iters[cpu]; +} + +static struct ring_buffer_event * +__peek_event(struct trace_remote_iterator *iter, int cpu, u64 *ts, unsigned long *lost_events) +{ + struct ring_buffer_event *rb_evt; + struct ring_buffer_iter *rb_iter; + + switch (iter->type) { + case TRI_CONSUMING: + return ring_buffer_peek(iter->remote->trace_buffer, cpu, ts, lost_events); + case TRI_NONCONSUMING: + rb_iter = __get_rb_iter(iter, cpu); + rb_evt = ring_buffer_iter_peek(rb_iter, ts); + if (!rb_evt) + return NULL; + + *lost_events = ring_buffer_iter_dropped(rb_iter); + + return rb_evt; + } + + return NULL; +} + static bool trace_remote_iter_read_event(struct trace_remote_iterator *iter) { struct trace_buffer *trace_buffer = iter->remote->trace_buffer; @@ -314,7 +490,7 @@ static bool trace_remote_iter_read_event(struct trace_remote_iterator *iter) if (ring_buffer_empty_cpu(trace_buffer, cpu)) return false; - if (!ring_buffer_peek(trace_buffer, cpu, &iter->ts, &iter->lost_events)) + if (!__peek_event(iter, cpu, &iter->ts, &iter->lost_events)) return false; iter->evt_cpu = cpu; @@ -329,7 +505,7 @@ static bool trace_remote_iter_read_event(struct trace_remote_iterator *iter) if (ring_buffer_empty_cpu(trace_buffer, cpu)) continue; - if (!ring_buffer_peek(trace_buffer, cpu, &ts, &lost_events)) + if (!__peek_event(iter, cpu, &ts, &lost_events)) continue; if (ts >= iter->ts) @@ -343,7 +519,21 @@ static bool trace_remote_iter_read_event(struct trace_remote_iterator *iter) return iter->ts != U64_MAX; } -static int trace_remote_iter_print(struct trace_remote_iterator *iter) +static void trace_remote_iter_move(struct trace_remote_iterator *iter) +{ + struct trace_buffer *trace_buffer = iter->remote->trace_buffer; + + switch (iter->type) { + case TRI_CONSUMING: + ring_buffer_consume(trace_buffer, iter->evt_cpu, NULL, NULL); + break; + case TRI_NONCONSUMING: + ring_buffer_iter_advance(__get_rb_iter(iter, iter->evt_cpu)); + break; + } +} + +static int trace_remote_iter_print_event(struct trace_remote_iterator *iter) { unsigned long usecs_rem; u64 ts = iter->ts; @@ -371,7 +561,11 @@ static int trace_pipe_open(struct inode *inode, struct file *filp) cpu = (long)inode->i_cdev - 1; guard(mutex)(&remote->lock); - iter = trace_remote_iter(remote, cpu); + + iter = trace_remote_iter(remote, cpu, TRI_CONSUMING); + if (IS_ERR(iter)) + return PTR_ERR(iter); + filp->private_data = iter; return IS_ERR(iter) ? PTR_ERR(iter) : 0; @@ -406,6 +600,8 @@ static ssize_t trace_pipe_read(struct file *filp, char __user *ubuf, size_t cnt, if (ret < 0) return ret; + trace_remote_iter_read_start(iter); + while (trace_remote_iter_read_event(iter)) { int prev_len = iter->seq.seq.len; @@ -414,9 +610,11 @@ static ssize_t trace_pipe_read(struct file *filp, char __user *ubuf, size_t cnt, break; } - ring_buffer_consume(trace_buffer, iter->evt_cpu, NULL, NULL); + trace_remote_iter_move(iter); } + trace_remote_iter_read_finished(iter); + goto copy_to_user; } @@ -426,6 +624,119 @@ static const struct file_operations trace_pipe_fops = { .release = trace_pipe_release, }; +static void *trace_seq_start(struct seq_file *m, loff_t *pos) +{ + struct trace_remote_iterator *iter = m->private; + loff_t i = *pos; + + if (!iter) + return NULL; + + if (iter->pos <= *pos) { + do { + if (!trace_remote_iter_read_event(iter)) + return NULL; + + trace_remote_iter_move(iter); + iter->pos++; + } while (i--); + } + + return iter; +} + +static void *trace_seq_next(struct seq_file *m, void *v, loff_t *pos) +{ + struct trace_remote_iterator *iter = m->private; + + ++*pos; + + if (!iter || !trace_remote_iter_read_event(iter)) + return NULL; + + trace_remote_iter_move(iter); + iter->pos++; + + return iter; +} + +static int trace_seq_show(struct seq_file *m, void *v) +{ + struct trace_remote_iterator *iter = v; + + trace_seq_init(&iter->seq); + + if (trace_remote_iter_print_event(iter)) { + seq_printf(m, "[EVENT %d PRINT TOO BIG]\n", iter->evt->id); + return 0; + } + + return trace_print_seq(m, &iter->seq); +} + +static void trace_seq_stop(struct seq_file *s, void *v) { } + +static const struct seq_operations trace_seq_ops = { + .start = trace_seq_start, + .next = trace_seq_next, + .show = trace_seq_show, + .stop = trace_seq_stop, +}; + +static int trace_open(struct inode *inode, struct file *filp) +{ + struct trace_remote *remote = inode->i_private; + struct trace_remote_iterator *iter = NULL; + int cpu = RING_BUFFER_ALL_CPUS; + int ret; + + if (!(filp->f_mode & FMODE_READ)) + return 0; + + if (inode->i_cdev) + cpu = (long)inode->i_cdev - 1; + + guard(mutex)(&remote->lock); + + iter = trace_remote_iter(remote, cpu, TRI_NONCONSUMING); + if (IS_ERR(iter)) + return PTR_ERR(iter); + + ret = seq_open(filp, &trace_seq_ops); + if (ret) { + trace_remote_iter_free(iter); + return ret; + } + + if (iter) + trace_remote_iter_read_start(iter); + + ((struct seq_file *)filp->private_data)->private = (void *)iter; + + return 0; +} + +static int trace_release(struct inode *inode, struct file *filp) +{ + struct trace_remote_iterator *iter; + + if (!(filp->f_mode & FMODE_READ)) + return 0; + + iter = ((struct seq_file *)filp->private_data)->private; + seq_release(inode, filp); + + if (!iter) + return 0; + + guard(mutex)(&iter->remote->lock); + + trace_remote_iter_read_finished(iter); + trace_remote_iter_free(iter); + + return 0; +} + static ssize_t trace_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) { struct inode *inode = file_inode(filp); @@ -443,7 +754,11 @@ static ssize_t trace_write(struct file *filp, const char __user *ubuf, size_t cn } static const struct file_operations trace_fops = { + .open = trace_open, .write = trace_write, + .read = seq_read, + .read_iter = seq_read_iter, + .release = trace_release, }; static int trace_remote_init_tracefs(const char *name, struct trace_remote *remote) @@ -532,6 +847,7 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, remote->trace_buffer_size = 7 << 10; remote->poll_ms = 100; mutex_init(&remote->lock); + init_rwsem(&remote->reader_lock); if (trace_remote_init_tracefs(name, remote)) { kfree(remote); -- 2.51.2.1041.gc1ab5b90ca-goog