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: <20190401170046.616280687@linuxfoundation.org>
Date:   Mon,  1 Apr 2019 19:03:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kohji Okuno <okuno.kohji@...panasonic.com>,
        Shawn Guo <shawnguo@...nel.org>
Subject: [PATCH 3.18 49/50] ARM: imx6q: cpuidle: fix bug that CPU might not wake up at expected time

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kohji Okuno <okuno.kohji@...panasonic.com>

commit 91740fc8242b4f260cfa4d4536d8551804777fae upstream.

In the current cpuidle implementation for i.MX6q, the CPU that sets
'WAIT_UNCLOCKED' and the CPU that returns to 'WAIT_CLOCKED' are always
the same. While the CPU that sets 'WAIT_UNCLOCKED' is in IDLE state of
"WAIT", if the other CPU wakes up and enters IDLE state of "WFI"
istead of "WAIT", this CPU can not wake up at expired time.
 Because, in the case of "WFI", the CPU must be waked up by the local
timer interrupt. But, while 'WAIT_UNCLOCKED' is set, the local timer
is stopped, when all CPUs execute "wfi" instruction. As a result, the
local timer interrupt is not fired.
 In this situation, this CPU will wake up by IRQ different from local
timer. (e.g. broacast timer)

So, this fix changes CPU to return to 'WAIT_CLOCKED'.

Signed-off-by: Kohji Okuno <okuno.kohji@...panasonic.com>
Fixes: e5f9dec8ff5f ("ARM: imx6q: support WAIT mode using cpuidle")
Cc: <stable@...r.kernel.org>
Signed-off-by: Shawn Guo <shawnguo@...nel.org>
Signed-off-by: Kohji Okuno <okuno.kohji@...panasonic.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/mach-imx/cpuidle-imx6q.c |   27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

--- a/arch/arm/mach-imx/cpuidle-imx6q.c
+++ b/arch/arm/mach-imx/cpuidle-imx6q.c
@@ -15,30 +15,23 @@
 #include "cpuidle.h"
 #include "hardware.h"
 
-static atomic_t master = ATOMIC_INIT(0);
-static DEFINE_SPINLOCK(master_lock);
+static int num_idle_cpus = 0;
+static DEFINE_SPINLOCK(cpuidle_lock);
 
 static int imx6q_enter_wait(struct cpuidle_device *dev,
 			    struct cpuidle_driver *drv, int index)
 {
-	if (atomic_inc_return(&master) == num_online_cpus()) {
-		/*
-		 * With this lock, we prevent other cpu to exit and enter
-		 * this function again and become the master.
-		 */
-		if (!spin_trylock(&master_lock))
-			goto idle;
+	spin_lock(&cpuidle_lock);
+	if (++num_idle_cpus == num_online_cpus())
 		imx6q_set_lpm(WAIT_UNCLOCKED);
-		cpu_do_idle();
-		imx6q_set_lpm(WAIT_CLOCKED);
-		spin_unlock(&master_lock);
-		goto done;
-	}
+	spin_unlock(&cpuidle_lock);
 
-idle:
 	cpu_do_idle();
-done:
-	atomic_dec(&master);
+
+	spin_lock(&cpuidle_lock);
+	if (num_idle_cpus-- == num_online_cpus())
+		imx6q_set_lpm(WAIT_CLOCKED);
+	spin_unlock(&cpuidle_lock);
 
 	return index;
 }


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ