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 A84D123CB; Wed, 28 May 2025 00:31:19 +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=1748392279; cv=none; b=JZSLO+RHI3EETy27afEgN2cLaLYXT9kfwDx4nvRwFoZIyKkdeAQ7LZdTCiKF2k0P75xXaoGHs2Hp0G1culWZdhBa6mlM0qijUuzZbGNJcN6XB1gmugOFrwXda9pAbEk4QYOxOrpXQWyK/NZ2Rjith/oi//vx5h78Z1i1QfEELiw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748392279; c=relaxed/simple; bh=M6A45JnFOKhyL13s3EAIlzuklRV8jx57NggH6mzCtGg=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=owuoTxa4OIlpyJYX3mxlsQUEOASinCqAK2xNdWXzIXZf3p6CuguzSmjBSVSjeGmmCAjSrjI9J5JucVchMXHD+SDn88qazlRpMwvyClxF3hsSKOkfgEPecyoM5z4bleWraiooetINsegg73IdkcBQPDjG5TLhrGuYLw1lELohk48= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LhFa+PSf; 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="LhFa+PSf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34089C4CEE9; Wed, 28 May 2025 00:31:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748392279; bh=M6A45JnFOKhyL13s3EAIlzuklRV8jx57NggH6mzCtGg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=LhFa+PSf8KqoIrFCRUq2WFGiIZ+oYlFl1KbnEQyj414uHH7iG4MQDU2ecb9Cp/8f4 70WgrBeA8p9nwH6Huwcgvv+b/3d7Drmn74W1pDtH+FYkSQYRfpeJtA+0mDqCNHF2Go 6mdQYTzoODUKr6PB6/pROqQQBsNiFGyONgROqU5Ik4e5+NPk4bn/0K8vvzhAPBKLpn +GlKjhcpKTvITvpI+y2ZedpmSKwM0ZXNhQpIPApTNjSiaf14Il2yfFkLjbZw4mxw8k tiA+pUo2+t6VZpQ43BqE66d/jIfrUzfdPuCosENF084M3zNP/rjzjOZgudGauKodeV vtQDhlJVL/aBQ== Date: Wed, 28 May 2025 09:31:16 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: LKML , Linux Trace Kernel , Masami Hiramatsu , Mathieu Desnoyers Subject: Re: [PATCH] ring-buffer: Simplify ring_buffer_read_page() with guard() Message-Id: <20250528093116.2451fe1b1ebad2f457594c57@kernel.org> In-Reply-To: <20250527145216.0187cf36@gandalf.local.home> References: <20250527145216.0187cf36@gandalf.local.home> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 27 May 2025 14:52:16 -0400 Steven Rostedt wrote: > From: Steven Rostedt > > The function ring_buffer_read_page() had two gotos. One was simply > returning "ret" and the other was unlocking the reader_lock. > > There's no reason to use goto to simply return the "ret" variable. Instead > just return the value. > > The jump to the unlocking of the reader_lock can be replaced by > guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock). > > With these two changes the "ret" variable is no longer used and can be > removed. The return value on non-error is what was read and is stored in > the "read" variable. > Looks good to me. Reviewed-by: Masami Hiramatsu (Google) Thanks! > Signed-off-by: Steven Rostedt (Google) > --- > kernel/trace/ring_buffer.c | 28 +++++++++++----------------- > 1 file changed, 11 insertions(+), 17 deletions(-) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 0b21d64e90c8..897ce51d3bbf 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -6535,38 +6535,37 @@ int ring_buffer_read_page(struct trace_buffer *buffer, > struct buffer_data_page *bpage; > struct buffer_page *reader; > unsigned long missed_events; > - unsigned long flags; > unsigned int commit; > unsigned int read; > u64 save_timestamp; > - int ret = -1; > > if (!cpumask_test_cpu(cpu, buffer->cpumask)) > - goto out; > + return -1; > > /* > * If len is not big enough to hold the page header, then > * we can not copy anything. > */ > if (len <= BUF_PAGE_HDR_SIZE) > - goto out; > + return -1; > > len -= BUF_PAGE_HDR_SIZE; > > if (!data_page || !data_page->data) > - goto out; > + return -1; > + > if (data_page->order != buffer->subbuf_order) > - goto out; > + return -1; > > bpage = data_page->data; > if (!bpage) > - goto out; > + return -1; > > - raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); > + guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock); > > reader = rb_get_reader_page(cpu_buffer); > if (!reader) > - goto out_unlock; > + return -1; > > event = rb_reader_event(cpu_buffer); > > @@ -6600,7 +6599,7 @@ int ring_buffer_read_page(struct trace_buffer *buffer, > if (full && > (!read || (len < (commit - read)) || > cpu_buffer->reader_page == cpu_buffer->commit_page)) > - goto out_unlock; > + return -1; > > if (len > (commit - read)) > len = (commit - read); > @@ -6609,7 +6608,7 @@ int ring_buffer_read_page(struct trace_buffer *buffer, > size = rb_event_ts_length(event); > > if (len < size) > - goto out_unlock; > + return -1; > > /* save the current timestamp, since the user will need it */ > save_timestamp = cpu_buffer->read_stamp; > @@ -6667,7 +6666,6 @@ int ring_buffer_read_page(struct trace_buffer *buffer, > if (reader->real_end) > local_set(&bpage->commit, reader->real_end); > } > - ret = read; > > cpu_buffer->lost_events = 0; > > @@ -6694,11 +6692,7 @@ int ring_buffer_read_page(struct trace_buffer *buffer, > if (commit < buffer->subbuf_size) > memset(&bpage->data[commit], 0, buffer->subbuf_size - commit); > > - out_unlock: > - raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); > - > - out: > - return ret; > + return read; > } > EXPORT_SYMBOL_GPL(ring_buffer_read_page); > > -- > 2.47.2 > -- Masami Hiramatsu (Google)