linux-kernel - [PATCH 2/2] cpuidle / menu: Return error code if there are no suitable states

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6832089.A5AOPipfbA@vostro.rjw.lan>
Date:	Sun, 27 Apr 2014 14:55:30 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Linux PM list <linux-pm@...r.kernel.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	'Daniel Lezcano' <daniel.lezcano@...aro.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 2/2] cpuidle / menu: Return error code if there are no suitable states

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

If there is a PM QoS latency limit and all of the sufficiently shallow
C-states are disabled, the cpuidle menu governor returns 0 which on
some systems is CPUIDLE_DRIVER_STATE_START and shouldn't be returned
if that C-state has been disabled.

Fix the issue by modifying the menu governor to return an error code
in such situations.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpuidle/governors/menu.c |    2 +-
 include/linux/cpuidle.h          |    2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/cpuidle/governors/menu.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governors/menu.c
+++ linux-pm/drivers/cpuidle/governors/menu.c
@@ -296,7 +296,7 @@ static int menu_select(struct cpuidle_dr
 		data->needs_update = 0;
 	}
 
-	data->last_state_idx = 0;
+	data->last_state_idx = CPUIDLE_DRIVER_STATE_POLL;
 
 	/* Special case when user has set very strict latency requirement */
 	if (unlikely(latency_req == 0))
Index: linux-pm/include/linux/cpuidle.h
===================================================================
--- linux-pm.orig/include/linux/cpuidle.h
+++ linux-pm/include/linux/cpuidle.h
@@ -217,8 +217,10 @@ static inline int cpuidle_register_gover
 
 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 #define CPUIDLE_DRIVER_STATE_START	1
+#define CPUIDLE_DRIVER_STATE_POLL	0
 #else
 #define CPUIDLE_DRIVER_STATE_START	0
+#define CPUIDLE_DRIVER_STATE_POLL	(-ENXIO)
 #endif
 
 #endif /* _LINUX_CPUIDLE_H */

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/