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From: Arnd Bergmann <arnd@arndb.de>
To: Andrew Morton <akpm@linux-foundation.org>,
	Mark Brown <broonie@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>,
	Tony Lindgren <tony@atomide.com>,
	Michael Grzeschik <m.grzeschik@pengutronix.de>,
	Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>,
	"Alex A. Mihaylov" <minimumlaw@rambler.ru>,
	linux-kernel@vger.kernel.org
Subject: [PATCH] [v2] iopoll: avoid -Wint-in-bool-context warning
Date: Wed, 26 Jul 2017 15:37:32 +0200
Message-ID: <20170726133756.2161367-1-arnd@arndb.de> (raw)

When we pass the result of a multiplication as the timeout or
the delay, we can get a warning:

drivers/mmc/host/bcm2835.c:596:149: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]
drivers/mfd/arizona-core.c:247:195: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]
drivers/gpu/drm/sun4i/sun4i_hdmi_i2c.c:49:27: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]

The warning is a bit questionable inside of a macro, but this
is intentional on the side of the gcc developers. It is also
an indication of another problem: we evaluate the timeout
and sleep arguments multiple times, which can have undesired
side-effects when those are complex expressions.

This changes the three iopoll variants to use local variables
for storing copies of the timeouts. This adds some more type
safety, and avoids both the double-evaluation and the gcc
warning.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81484
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v2: - use temporary variables instead of zero-comparison, to
      avoid double evaluation
    - also address the delay, not just timout handling
---
 include/linux/iopoll.h | 24 +++++++++++++++---------
 include/linux/regmap.h | 12 +++++++-----
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/include/linux/iopoll.h b/include/linux/iopoll.h
index d29e1e21bf3f..b1d861caca16 100644
--- a/include/linux/iopoll.h
+++ b/include/linux/iopoll.h
@@ -42,18 +42,21 @@
  */
 #define readx_poll_timeout(op, addr, val, cond, sleep_us, timeout_us)	\
 ({ \
-	ktime_t timeout = ktime_add_us(ktime_get(), timeout_us); \
-	might_sleep_if(sleep_us); \
+	u64 __timeout_us = (timeout_us); \
+	unsigned long __sleep_us = (sleep_us); \
+	ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
+	might_sleep_if((__sleep_us) != 0); \
 	for (;;) { \
 		(val) = op(addr); \
 		if (cond) \
 			break; \
-		if (timeout_us && ktime_compare(ktime_get(), timeout) > 0) { \
+		if (__timeout_us && \
+		    ktime_compare(ktime_get(), __timeout) > 0) { \
 			(val) = op(addr); \
 			break; \
 		} \
-		if (sleep_us) \
-			usleep_range((sleep_us >> 2) + 1, sleep_us); \
+		if (__sleep_us) \
+			usleep_range((__sleep_us >> 2) + 1, __sleep_us); \
 	} \
 	(cond) ? 0 : -ETIMEDOUT; \
 })
@@ -77,17 +80,20 @@
  */
 #define readx_poll_timeout_atomic(op, addr, val, cond, delay_us, timeout_us) \
 ({ \
-	ktime_t timeout = ktime_add_us(ktime_get(), timeout_us); \
+	u64 __timeout_us = (timeout_us); \
+	unsigned long __delay_us = (delay_us); \
+	ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
 	for (;;) { \
 		(val) = op(addr); \
 		if (cond) \
 			break; \
-		if (timeout_us && ktime_compare(ktime_get(), timeout) > 0) { \
+		if (__timeout_us && \
+		    ktime_compare(ktime_get(), __timeout) > 0) { \
 			(val) = op(addr); \
 			break; \
 		} \
-		if (delay_us) \
-			udelay(delay_us);	\
+		if (__delay_us) \
+			udelay(__delay_us);	\
 	} \
 	(cond) ? 0 : -ETIMEDOUT; \
 })
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 1474ab0a3922..a4d30c877f6b 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -120,22 +120,24 @@ struct reg_sequence {
  */
 #define regmap_read_poll_timeout(map, addr, val, cond, sleep_us, timeout_us) \
 ({ \
-	ktime_t __timeout = ktime_add_us(ktime_get(), timeout_us); \
+	u64 __timeout_us = (timeout_us); \
+	unsigned long __sleep_us = (sleep_us); \
+	ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
 	int __ret; \
-	might_sleep_if(sleep_us); \
+	might_sleep_if(__sleep_us); \
 	for (;;) { \
 		__ret = regmap_read((map), (addr), &(val)); \
 		if (__ret) \
 			break; \
 		if (cond) \
 			break; \
-		if ((timeout_us) && \
+		if (__timeout_us && \
 		    ktime_compare(ktime_get(), __timeout) > 0) { \
 			__ret = regmap_read((map), (addr), &(val)); \
 			break; \
 		} \
-		if (sleep_us) \
-			usleep_range(((sleep_us) >> 2) + 1, sleep_us); \
+		if (__sleep_us) \
+			usleep_range((__sleep_us >> 2) + 1, __sleep_us); \
 	} \
 	__ret ?: ((cond) ? 0 : -ETIMEDOUT); \
 })
-- 
2.9.0

             reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-26 13:37 Arnd Bergmann [this message]
2017-07-26 14:28 ` Mark Brown
2017-07-26 21:39   ` Andrew Morton
2017-07-27  9:53     ` Mark Brown
2017-07-26 21:38 ` Andrew Morton
2017-07-26 21:41   ` Arnd Bergmann

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