From patchwork Tue Dec 12 10:12:42 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: 13488870 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=nabijaczleweli.xyz header.i=@nabijaczleweli.xyz header.b="OT4OnGfp" Received: from tarta.nabijaczleweli.xyz (tarta.nabijaczleweli.xyz [139.28.40.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC15C10B; Tue, 12 Dec 2023 02:12:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=nabijaczleweli.xyz; s=202305; t=1702375963; bh=Lx01uUzZBLjfFlGQlKARFoT+Vf/QEeNIG29aSuy6Lf8=; h=Date:From:To:Subject:References:In-Reply-To:From; b=OT4OnGfpCidozTgeKJqlenrtbf0JerI1R/jU8yP204BjK4j3qeUs4ZqZNwq+f6H// wKV4HqXL7mYXXFJBLq2OKLvweJzrd2nRxE/rO5JGD4Ud/xGcZeyQuVEh6jmP1Udhog F1sTysJ+py9xrbtTHlxfK1QRFaZU0qzUB2Zj4tlnMrRM/ceBvOATJsNlsbAVtek1xP ouydr8agHAM56ic655re4rEW/1CWxSZE2nbSX6g89ldVK3ux4shwpRzDKF+qQVtqQd ph+hT5GDTBF728he4SOcBE2bdo9J9iPxtaP3Xf5qRpwFLPN20bh99gPmenALHXd0Oz N1dY4hhdd8a4Q== Received: from tarta.nabijaczleweli.xyz (unknown [192.168.1.250]) by tarta.nabijaczleweli.xyz (Postfix) with ESMTPSA id 0700D12A7C; Tue, 12 Dec 2023 11:12:43 +0100 (CET) Date: Tue, 12 Dec 2023 11:12:42 +0100 From: Ahelenia =?utf-8?q?Ziemia=C5=84ska?= To: Steven Rostedt , Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH RESEND 04/11] tracing: tracing_buffers_splice_read: behave as-if non-blocking I/O Message-ID: <11b84f2e4e5eaad501ff7b2bb03e2ad2f25ecdf14.1697486714.git.nabijaczleweli@nabijaczleweli.xyz> User-Agent: NeoMutt/20231103 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: <1cover.1697486714.git.nabijaczleweli@nabijaczleweli.xyz> 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;