linux-kernel - [PATCH 1/2] coccinelle: api/stream_open: treat all wait

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Date:   Sun, 23 Jun 2019 07:28:53 +0000
From:   Kirill Smelkov <kirr@...edi.com>
To:     <cocci@...teme.lip6.fr>, <linux-kernel@...r.kernel.org>
Cc:     Kirill Smelkov <kirr@...edi.com>,
        Julia Lawall <Julia.Lawall@...6.fr>,
        Logan Gunthorpe <logang@...tatee.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Bjorn Helgaas <helgaas@...nel.org>
Subject: [PATCH 1/2] coccinelle: api/stream_open: treat all wait_.*() calls as blocking

Previously steam_open.cocci was treating only wait_event_.* - e.g.
wait_event_interruptible - as a blocking operation. However e.g.
wait_for_completion_interruptible is also blocking, and so from this
point of view it would be more logical to treat all wait_.* as a
blocking point.

The logic of this change actually came up for real when
drivers/pci/switch/switchtec.c changed from using
wait_event_interruptible to wait_for_completion_interruptible:

	https://lore.kernel.org/linux-pci/20190413170056.GA11293@deco.navytux.spb.ru/
	https://lore.kernel.org/linux-pci/20190415145456.GA15280@deco.navytux.spb.ru/
	https://lore.kernel.org/linux-pci/20190415154102.GB17661@deco.navytux.spb.ru/

For a driver that uses nonseekable_open with read/write having stream
semantic and read also calling e.g. wait_for_completion_interruptible,
running stream_open.cocci before this patch would produce:

	WARNING: <driver>_fops: .read() and .write() have stream semantic; safe to change nonseekable_open -> stream_open.

while after this patch it will report:

	ERROR: <driver>_fops: .read() can deadlock .write(); change nonseekable_open -> stream_open to fix.

Cc: Julia Lawall <Julia.Lawall@...6.fr>
Cc: Logan Gunthorpe <logang@...tatee.com>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Bjorn Helgaas <helgaas@...nel.org>
Signed-off-by: Kirill Smelkov <kirr@...edi.com>
---
 scripts/coccinelle/api/stream_open.cocci | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/scripts/coccinelle/api/stream_open.cocci b/scripts/coccinelle/api/stream_open.cocci
index 350145da7669..12ce18fa6b74 100644
--- a/scripts/coccinelle/api/stream_open.cocci
+++ b/scripts/coccinelle/api/stream_open.cocci
@@ -35,11 +35,11 @@ type loff_t;
 // a function that blocks
 @ blocks @
 identifier block_f;
-identifier wait_event =~ "^wait_event_.*";
+identifier wait =~ "^wait_.*";
 @@
   block_f(...) {
     ... when exists
-    wait_event(...)
+    wait(...)
     ... when exists
   }
 
@@ -49,12 +49,12 @@ identifier wait_event =~ "^wait_event_.*";
 // XXX currently reader_blocks supports only direct and 1-level indirect cases.
 @ reader_blocks_direct @
 identifier stream_reader.readstream;
-identifier wait_event =~ "^wait_event_.*";
+identifier wait =~ "^wait_.*";
 @@
   readstream(...)
   {
     ... when exists
-    wait_event(...)
+    wait(...)
     ... when exists
   }
 
-- 
2.20.1