From mboxrd@z Thu Jan 1 00:00:00 1970 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 F343426F47A; Tue, 8 Apr 2025 12:58:36 +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=1744117117; cv=none; b=YJ9+tQ0spKBmX8rwCC1yxvTU/MEpoO69R9PqPPKd/I1UqnWLvf33/mywFrQRV8WYH7/+MFPpyiObodLIiVfpwZD3Op4/0i1cpNtkCLWa+Bm/4Y22u9th68oXs7a8XecrtrE7zIefFFbJt7twvI4M9yFwPHHaN2ZdkyJEgTdvbQA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744117117; c=relaxed/simple; bh=VQw8sujYK+vN3jZwHm9Mmn5nCvdFY+TrtPPRsfqrjGc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y5jEd0h8W/J4CzDzapoXevZAWT18wIFtcin+J/Un50U26fTqAaokWFBjr/NmKyj8kygytvqgQvNHk+OzCEh7CeJwpRYcd1zl0usWRgaVZ7vWqqvQoglHTTRDxVlMqq1SjFRvMAMsmRNgmkGFKVg7C41g8XJHgslW/H8nIxR/N3Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eo7R19dD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="eo7R19dD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 582FBC4CEEA; Tue, 8 Apr 2025 12:58:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744117116; bh=VQw8sujYK+vN3jZwHm9Mmn5nCvdFY+TrtPPRsfqrjGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eo7R19dDKcEp8MtU5165zGwsS5h+J4Jyny4dDw3GKHg93jR1UNwiy4CigYFew/FNf cf3L0CVxDa+IZ3GS3M+T4BjfNCENwVKN0Pj64jpaz/bzzU8ecSH6dA6KJ999i9Xg+u jSOJHiVsD7zF6wbbF0aGRvf0h4S9PHjZOlbxSHqo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Shuah Khan , Mathieu Desnoyers , "Masami Hiramatsu (Google)" , Tom Zanussi , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 6.12 351/423] tracing/hist: Add poll(POLLIN) support on hist file Date: Tue, 8 Apr 2025 12:51:17 +0200 Message-ID: <20250408104854.022680433@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104845.675475678@linuxfoundation.org> References: <20250408104845.675475678@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Masami Hiramatsu (Google) [ Upstream commit 1bd13edbbed6e7e396f1aab92b224a4775218e68 ] 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 it is not a good idea to peek at the `trace` for an event that randomly happens. And `trace_pipe` is not coming back until a page is filled with events. This allows a user to wait for a specific event on the `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 a read() happens on that 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. Cc: Shuah Khan Cc: Mathieu Desnoyers Link: https://lore.kernel.org/173527247756.464571.14236296701625509931.stgit@devnote2 Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Tom Zanussi Signed-off-by: Steven Rostedt (Google) Stable-dep-of: 0b4ffbe4888a ("tracing: Correct the refcount if the hist/hist_debug file fails to open") Signed-off-by: Sasha Levin --- include/linux/trace_events.h | 14 +++++++ kernel/trace/trace_events.c | 14 +++++++ kernel/trace/trace_events_hist.c | 70 ++++++++++++++++++++++++++++++-- 3 files changed, 95 insertions(+), 3 deletions(-) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 77769ff505444..fcf5a64d5cfe2 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -689,6 +689,20 @@ 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 ea9b44847ce6b..29eba68e07859 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -3111,6 +3111,20 @@ 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 5d344bc690d99..9e33cd2a73b5c 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; guard(mutex)(&event_mutex); - event_file = event_file_file(m->private); + event_file = event_file_file(hist_file->file); if (unlikely(!event_file)) return -ENODEV; @@ -5609,27 +5632,68 @@ 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); + return 0; } +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; + + guard(mutex)(&event_mutex); + + event_file = event_file_data(file); + if (!event_file) + return EPOLLERR; + + hist_poll_wait(file, wait); + + if (hist_file->last_read != get_hist_hit_count(event_file)) + return EPOLLIN | EPOLLRDNORM; + + return 0; +} + +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 -- 2.39.5