From patchwork Mon Oct 16 20:35:45 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?b?0L3QsNCx?= X-Patchwork-Id: 13424133 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 8A39D358B1 for ; Mon, 16 Oct 2023 20:35:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=nabijaczleweli.xyz header.i=@nabijaczleweli.xyz header.b="jYyfhEbJ" Received: from tarta.nabijaczleweli.xyz (tarta.nabijaczleweli.xyz [139.28.40.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1EE35F9; Mon, 16 Oct 2023 13:35:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=nabijaczleweli.xyz; s=202305; t=1697488545; bh=M3/tVO1jPiOOO1Rw82ko0E0+3twLTEqXefGMw9ogJ9c=; h=Date:From:Cc:Subject:References:In-Reply-To:From; b=jYyfhEbJKEMbOcqostzxf+q73l4ZaJN6lOf9bdtVSWBOPf+msOlGFpNFJVUsC6+QG 4wJk7QZj/bAAHrNWwhLZuaEVwhM5Iau+GJ3ojMT0KmcjbZoVDP8Skr8cgtWqiuJHNN pMZ7Lvlf8sfXBY000Uy1ucYtx/WVcKldmqPDCM1xc0Ewjiq3/kxnKcdUStKYsI5EZQ g1tOMXu8arK3rnoQylY8ZPA5AvYphy71K/rwO1J1Qs3jVbucbNUusKHp5iPIlf3PZP Ten/sO9sDaOD7Sh0aRYfwshmiwXykfQDyItYBVGMYi+QjMKL0/38X1D1bhgw/zCn5S wXaLEXXF1FoVw== Received: from tarta.nabijaczleweli.xyz (unknown [192.168.1.250]) by tarta.nabijaczleweli.xyz (Postfix) with ESMTPSA id 4B34D10410; Mon, 16 Oct 2023 22:35:45 +0200 (CEST) Date: Mon, 16 Oct 2023 22:35:45 +0200 From: Ahelenia =?utf-8?q?Ziemia=C5=84ska?= Cc: Steven Rostedt , Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH 04/11] tracing: tracing_buffers_splice_read: behave as-if non-blocking I/O Message-ID: <1b84f2e4e5eaad501ff7b2bb03e2ad2f25ecdf14.1697486714.git.nabijaczleweli@nabijaczleweli.xyz> References: Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20231006 X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MISSING_HEADERS, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Otherwise we risk sleeping with the pipe locked for indeterminate lengths of time. Link: https://lore.kernel.org/linux-fsdevel/qk6hjuam54khlaikf2ssom6custxf5is2ekkaequf4hvode3ls@zgf7j5j4ubvw/t/#u Signed-off-by: Ahelenia Ziemiańska --- kernel/trace/trace.c | 32 ++++---------------------------- 1 file changed, 4 insertions(+), 28 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index abaaf516fcae..9be7a4c0a3ca 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8477,7 +8477,6 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, if (splice_grow_spd(pipe, &spd)) return -ENOMEM; - again: trace_access_lock(iter->cpu_file); entries = ring_buffer_entries_cpu(iter->array_buffer->buffer, iter->cpu_file); @@ -8528,35 +8527,12 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, /* did we read anything? */ if (!spd.nr_pages) { - long wait_index; - - if (ret) - goto out; - - ret = -EAGAIN; - if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK)) - goto out; - - wait_index = READ_ONCE(iter->wait_index); - - ret = wait_on_pipe(iter, iter->tr->buffer_percent); - if (ret) - goto out; - - /* No need to wait after waking up when tracing is off */ - if (!tracer_tracing_is_on(iter->tr)) - goto out; - - /* Make sure we see the new wait_index */ - smp_rmb(); - if (wait_index != iter->wait_index) - goto out; - - goto again; + if (!ret) + ret = -EAGAIN; + } else { + ret = splice_to_pipe(pipe, &spd); } - ret = splice_to_pipe(pipe, &spd); -out: splice_shrink_spd(&spd); return ret;