From patchwork Wed Oct 16 10:49:24 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu \(Google\)" X-Patchwork-Id: 837125 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AFD8B20514B; Wed, 16 Oct 2024 10:49:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729075768; cv=none; b=gxBQuJ+k3u8G333LyshfTiiBYr9bhGXsnSiLPdOOd4CRB6XlRjapLYIm7G+3CDI8H+Xama2yHLTW7qQ8hWTGAYrZ7vlr+qmVtkpWDa5LSXnNST+1tj34Xe8PxYi6JX0TWY7BgZKKAvnj2bhplZSPNDPsKlGjhjo4Pig5UaqWMYs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729075768; c=relaxed/simple; bh=EFt2YqSmM2kHiH7ygo+ZURxSXzlTYOn0haPNawBOZTE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hW9scvwpwdbG9aGX1vHWFsYdYXsjss0wmqkcnhgW4MNu1VXsOy3OtR9HQeSzdZ1KSH8ZgfMroBBYKmlnRcOTV9Ff7swPxp6wcxYP2NKRv6/AQkDj5s7EfNuFpfa1JixqN/V0dDiF92SRkvy7VUKU0bqu/eqCBlBv967GBMx/GG4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pYvgApve; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pYvgApve" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F102C4CECD; Wed, 16 Oct 2024 10:49:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729075768; bh=EFt2YqSmM2kHiH7ygo+ZURxSXzlTYOn0haPNawBOZTE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pYvgApveNGA2j826YMumZFHPWPXbz+9rmLbpfgO1Fd/KvA/bd+gD7aOpoGX9mmQiN O5CyuE49p3QxhTrhLMb/+Vi7yOH6bXrUoQ5E2iq+7bEfIB3+KCUkgtg4Hw6zuocqQq 9tNCuE8AOIui6N02Z3JNtA2I2dY4KKNIAvHsf6+degd323/YY1+zBIetRFGTDuvmZ1 YxCZ8VOwwk1PMuBasNG6trJJhgZyXwVORLYXG2ao6iYb71n0+C9HlZUZQMH3n8Urbb Yt+DMPXLp+eG8maKFCFucYvd0L94oRkCXf9CB0j7CLRJwboCA8o5rU82dcuKgXyVEd +F67qHOxToMAg== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Shuah Khan Cc: Masami Hiramatsu , Tom Zanussi , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v6 1/3] tracing/hist: Add poll(POLLIN) support on hist file Date: Wed, 16 Oct 2024 19:49:24 +0900 Message-ID: <172907576461.470540.1954983717302445787.stgit@mhiramat.roam.corp.google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog In-Reply-To: <172907575534.470540.12941248697563459082.stgit@mhiramat.roam.corp.google.com> References: <172907575534.470540.12941248697563459082.stgit@mhiramat.roam.corp.google.com> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Masami Hiramatsu (Google) Add poll syscall support on the `hist` file. The Waiter will be waken up when the histogram is updated with POLLIN. Currently, there is no way to wait for a specific event in userspace. So user needs to peek the `trace` periodicaly, or wait on `trace_pipe`. But that is not good idea to peek the `trace` for the event randomely happens. And `trace_pipe` is not coming back until a page is filled with events. This allows user to wait for a specific events on `hist` file. User can set a histogram trigger on the event which they want to monitor. And poll() on its `hist` file. Since this poll() returns POLLIN, the next poll() will return soon unless you do read() on hist file. NOTE: To read the hist file again, you must set the file offset to 0, but just for monitoring the event, you may not need to read the histogram. Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Tom Zanussi --- Changes in v6: - Use a global poll irq_work and wait_queue. --- include/linux/trace_events.h | 14 +++++++ kernel/trace/trace_events.c | 14 +++++++ kernel/trace/trace_events_hist.c | 75 ++++++++++++++++++++++++++++++++++++-- 3 files changed, 100 insertions(+), 3 deletions(-) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 42bedcddd511..46c771a61f2a 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -685,6 +685,20 @@ struct trace_event_file { atomic_t tm_ref; /* trigger-mode reference counter */ }; +#ifdef CONFIG_HIST_TRIGGERS +extern struct irq_work hist_poll_work; +extern wait_queue_head_t hist_poll_wq; + +static inline void hist_poll_wakeup(void) +{ + if (wq_has_sleeper(&hist_poll_wq)) + irq_work_queue(&hist_poll_work); +} + +#define hist_poll_wait(file, wait) \ + poll_wait(file, &hist_poll_wq, wait) +#endif + #define __TRACE_EVENT_FLAGS(name, value) \ static int __init trace_init_flags_##name(void) \ { \ diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 7266ec2a4eea..0a7cb30043ef 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2972,6 +2972,20 @@ static bool event_in_systems(struct trace_event_call *call, return !*p || isspace(*p) || *p == ','; } +#ifdef CONFIG_HIST_TRIGGERS +/* + * Wake up waiter on the hist_poll_wq from irq_work because the hist trigger + * may happen in any context. + */ +static void hist_poll_event_irq_work(struct irq_work *work) +{ + wake_up_all(&hist_poll_wq); +} + +DEFINE_IRQ_WORK(hist_poll_work, hist_poll_event_irq_work); +DECLARE_WAIT_QUEUE_HEAD(hist_poll_wq); +#endif + static struct trace_event_file * trace_create_new_event(struct trace_event_call *call, struct trace_array *tr) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 5f9119eb7c67..107eaa0f40f1 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -5314,6 +5314,8 @@ static void event_hist_trigger(struct event_trigger_data *data, if (resolve_var_refs(hist_data, key, var_ref_vals, true)) hist_trigger_actions(hist_data, elt, buffer, rec, rbe, key, var_ref_vals); + + hist_poll_wakeup(); } static void hist_trigger_stacktrace_print(struct seq_file *m, @@ -5593,15 +5595,36 @@ static void hist_trigger_show(struct seq_file *m, n_entries, (u64)atomic64_read(&hist_data->map->drops)); } +struct hist_file_data { + struct file *file; + u64 last_read; +}; + +static u64 get_hist_hit_count(struct trace_event_file *event_file) +{ + struct hist_trigger_data *hist_data; + struct event_trigger_data *data; + u64 ret = 0; + + list_for_each_entry(data, &event_file->triggers, list) { + if (data->cmd_ops->trigger_type == ETT_EVENT_HIST) { + hist_data = data->private_data; + ret += atomic64_read(&hist_data->map->hits); + } + } + return ret; +} + static int hist_show(struct seq_file *m, void *v) { + struct hist_file_data *hist_file = m->private; struct event_trigger_data *data; struct trace_event_file *event_file; int n = 0, ret = 0; mutex_lock(&event_mutex); - event_file = event_file_file(m->private); + event_file = event_file_file(hist_file->file); if (unlikely(!event_file)) { ret = -ENODEV; goto out_unlock; @@ -5611,6 +5634,7 @@ static int hist_show(struct seq_file *m, void *v) if (data->cmd_ops->trigger_type == ETT_EVENT_HIST) hist_trigger_show(m, data, n++); } + hist_file->last_read = get_hist_hit_count(event_file); out_unlock: mutex_unlock(&event_mutex); @@ -5618,24 +5642,69 @@ static int hist_show(struct seq_file *m, void *v) return ret; } +static __poll_t event_hist_poll(struct file *file, struct poll_table_struct *wait) +{ + struct trace_event_file *event_file; + struct seq_file *m = file->private_data; + struct hist_file_data *hist_file = m->private; + __poll_t ret = 0; + + mutex_lock(&event_mutex); + + event_file = event_file_data(file); + if (!event_file) { + ret = EPOLLERR; + goto out_unlock; + } + + hist_poll_wait(file, wait); + + if (hist_file->last_read != get_hist_hit_count(event_file)) + ret = EPOLLIN | EPOLLRDNORM; + +out_unlock: + mutex_unlock(&event_mutex); + + return ret; +} + +static int event_hist_release(struct inode *inode, struct file *file) +{ + struct seq_file *m = file->private_data; + struct hist_file_data *hist_file = m->private; + + kfree(hist_file); + return tracing_single_release_file_tr(inode, file); +} + static int event_hist_open(struct inode *inode, struct file *file) { + struct hist_file_data *hist_file; int ret; ret = tracing_open_file_tr(inode, file); if (ret) return ret; + hist_file = kzalloc(sizeof(*hist_file), GFP_KERNEL); + if (!hist_file) + return -ENOMEM; + hist_file->file = file; + /* Clear private_data to avoid warning in single_open() */ file->private_data = NULL; - return single_open(file, hist_show, file); + ret = single_open(file, hist_show, hist_file); + if (ret) + kfree(hist_file); + return ret; } const struct file_operations event_hist_fops = { .open = event_hist_open, .read = seq_read, .llseek = seq_lseek, - .release = tracing_single_release_file_tr, + .release = event_hist_release, + .poll = event_hist_poll, }; #ifdef CONFIG_HIST_TRIGGERS_DEBUG