Message-ID: <20131127231541.GA8418@kahuna>
Date:	Wed, 27 Nov 2013 17:15:41 -0600
From:	Nishanth Menon <nm@...com>
To:	Sekhar Nori <nsekhar@...com>, <rjw@...ysocki.net>
CC:	Daniel Mack <zonque@...il.com>, <linux-omap@...r.kernel.org>,
	<joelf@...com>, <gururaja.hebbar@...com>, <balajitk@...com>,
	<s.neumann@...mfeld.com>, <Russ.Dill@...com>,
	<vaibhav.bedia@...il.com>, <linux-arm-kernel@...ts.infradead.org>,
	Kevin Hilman <khilman@...aro.org>, <Julia.Lawall@...6.fr>,
	<Gilles.Muller@...6.fr>, <nicolas.palix@...g.fr>, <mmarek@...e.cz>,
	<linux-kernel@...r.kernel.org>, <cocci@...teme.lip6.fr>,
	<rmk+kernel@....linux.org.uk>, <linux-pm@...r.kernel.org>
Subject: pm_runtime functions and IS_ERR_VALUE (was Re: [PATCH v6] ARM: omap:
 edma: add suspend suspend/resume hooks)

Change in subject line + wider forum

On 19:24-20131127, Sekhar Nori wrote:
> On Wednesday 27 November 2013 07:17 PM, Daniel Mack wrote:
> > On 11/27/2013 02:35 PM, Sekhar Nori wrote:
> >> On Monday 18 November 2013 03:49 AM, Daniel Mack wrote:
> >>> +static int edma_pm_suspend(struct device *dev)
> >>> +{
> >>> +	int j, r;
> >>> +
> >>> +	r = pm_runtime_get_sync(dev);
> >>> +	if (IS_ERR_VALUE(r)) {
> >>
> >> So IS_ERR_VALUE() is only for functions which may return a negative
> >> number outside of MAX_ERRNO as a success indication.
> >> pm_runtime_get_sync() does not appear to be one of them so just use"
> >>
> >> if (r < 0) { .. }
> > 
> > That's true. Thanks for catching this, I'll fix it. However, grepping
> > through the tree, there are quite a lot places where the same mistake is
> > made.
> 
> Yes, this is a common fallacy. Russell cleaned up a bunch of these a
> while back.

Thinking a little more on this front, to prevent recurrence and fixing
the ones we already have, how about something like the following
patch?

For example, on 3.13-rc1, with omap2plus_defconfig, I see the following:
http://pastebin.mozilla.org/3681911

-->8--
>From b7946d214fab72b2e18cd67eec01c377f1cddee8 Mon Sep 17 00:00:00 2001
From: Nishanth Menon <nm@...com>
Date: Wed, 27 Nov 2013 17:01:20 -0600
Subject: [RFC PATCH] scripts: Coccinelle script for pm_runtime_* return checks
 with IS_ERR_VALUE

As indicated by Sekhar in [1], there seems to be a tendency to use
IS_ERR_VALUE to check the error result for pm_runtime_* functions which
make no sense considering commit c48cd65 (ARM: OMAP: use consistent
error checking) - the error values can either be < 0 for error OR
0, 1 in cases where we have success.

So, setup a coccinelle script to help identify the same.

[1] http://marc.info/?t=138472678100003&r=1&w=2

Cc: Russell King <rmk+kernel@....linux.org.uk>
Reported-by: Sekhar Nori <nsekhar@...com>
Signed-off-by: Nishanth Menon <nm@...com>
---
 scripts/coccinelle/api/pm_runtime.cocci |  109 +++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 scripts/coccinelle/api/pm_runtime.cocci

diff --git a/scripts/coccinelle/api/pm_runtime.cocci b/scripts/coccinelle/api/pm_runtime.cocci
new file mode 100644
index 0000000..f01789e
--- /dev/null
+++ b/scripts/coccinelle/api/pm_runtime.cocci
@@ -0,0 +1,109 @@
+/// Make sure pm_runtime_* calls does not use unnecessary IS_ERR_VALUE
+//
+// Keywords: pm_runtime
+// Confidence: Medium
+// Copyright (C) 2013 Texas Instruments Incorporated - GPLv2.
+// URL: http://coccinelle.lip6.fr/
+// Options: --include-headers
+
+virtual patch
+virtual context
+virtual org
+virtual report
+
+//----------------------------------------------------------
+//  Detection
+//----------------------------------------------------------
+
+@...time_bad_err_handle exists@
+expression ret;
+@@
+(
+ret = \(pm_runtime_idle\|
+	pm_runtime_suspend\|
+	pm_runtime_autosuspend\|
+	pm_runtime_resume\|
+	pm_request_idle\|
+	pm_request_resume\|
+	pm_request_autosuspend\|
+	pm_runtime_get\|
+	pm_runtime_get_sync\|
+	pm_runtime_put\|
+	pm_runtime_put_autosuspend\|
+	pm_runtime_put_sync\|
+	pm_runtime_put_sync_suspend\|
+	pm_runtime_put_sync_autosuspend\|
+	pm_runtime_set_active\|
+	pm_schedule_suspend\|
+	pm_runtime_barrier\|
+	pm_generic_runtime_suspend\|
+	pm_generic_runtime_resume\)(...);
+...
+IS_ERR_VALUE(ret)
+...
+)
+
+//----------------------------------------------------------
+//  For context mode
+//----------------------------------------------------------
+
+@...ends on runtime_bad_err_handle && context@
+identifier pm_runtime_api;
+expression ret;
+@@
+(
+ret = pm_runtime_api(...);
+...
+* IS_ERR_VALUE(ret)
+...
+)
+
+//----------------------------------------------------------
+//  For patch mode
+//----------------------------------------------------------
+
+@...ends on runtime_bad_err_handle && patch@
+identifier pm_runtime_api;
+expression ret;
+@@
+(
+ret = pm_runtime_api(...);
+...
+- IS_ERR_VALUE(ret)
++ ret < 0
+...
+)
+
+//----------------------------------------------------------
+//  For org and report mode
+//----------------------------------------------------------
+
+@r depends on runtime_bad_err_handle exists@
+position p1, p2;
+identifier pm_runtime_api;
+expression ret;
+@@
+(
+ret = pm_runtime_api@p1(...);
+...
+IS_ERR_VALUE@p2(ret)
+...
+)
+
+@...ipt:python depends on org@
+p1 << r.p1;
+p2 << r.p2;
+pm_runtime_api << r.pm_runtime_api;
+@@
+
+cocci.print_main(pm_runtime_api,p1)
+cocci.print_secs("IS_ERR_VALUE",p2)
+
+@...ipt:python depends on report@
+p1 << r.p1;
+p2 << r.p2;
+pm_runtime_api << r.pm_runtime_api;
+@@
+
+msg = "%s returns < 0 as error. Unecessary IS_ERR_VALUE at line %s" % (pm_runtime_api, p2[0].line)
+coccilib.report.print_report(p1[0],msg)
-- 
1.7.9.5

-- 
Regards,
Nishanth Menon
--
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