| 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
| ||
|
Message-Id: <1423224113-10958-94-git-send-email-luis.henriques@canonical.com>
Date: Fri, 6 Feb 2015 12:01:11 +0000
From: Luis Henriques <luis.henriques@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Paul Osmialowski <p.osmialowsk@...sung.com>,
Wolfram Sang <wsa@...-dreams.de>,
Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 093/135] i2c: s3c2410: fix ABBA deadlock by keeping clock prepared
3.16.7-ckt6 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Paul Osmialowski <p.osmialowsk@...sung.com>
commit 34e81ad5f0b60007c95995eb7803da7e00c6c611 upstream.
This patch solves deadlock between clock prepare mutex and regmap mutex reported
by Tomasz Figa in [1] by implementing solution from [2]: "always leave the clock
of the i2c controller in a prepared state".
[1] https://lkml.org/lkml/2014/7/2/171
[2] https://lkml.org/lkml/2014/7/2/207
On each i2c transfer handled by s3c24xx_i2c_xfer(), clk_prepare_enable() was
called, which calls clk_prepare() then clk_enable(). clk_prepare() takes
prepare_lock mutex before proceeding. Note that i2c transfer functions are
invoked from many places in kernel, typically with some other additional lock
held.
It may happen that function on CPU1 (e.g. regmap_update_bits()) has taken a
mutex (i.e. regmap lock mutex) then it attempts i2c communication in order to
proceed (so it needs to obtain clock related prepare_lock mutex during transfer
preparation stage due to clk_prepare() call). At the same time other task on
CPU0 wants to operate on clock (e.g. to (un)prepare clock for some other reason)
so it has taken prepare_lock mutex.
CPU0: CPU1:
clk_disable_unused() regulator_disable()
clk_prepare_lock() map->lock(map->lock_arg)
regmap_read() s3c24xx_i2c_xfer()
map->lock(map->lock_arg) clk_prepare_lock()
Implemented solution from [2] leaves i2c clock prepared. Preparation is done in
s3c24xx_i2c_probe() function. Without this patch, it is immediately unprepared
by clk_disable_unprepare() call. I've replaced this call with clk_disable() and
I've added clk_unprepare() call in s3c24xx_i2c_remove().
The s3c24xx_i2c_xfer() function now uses clk_enable() instead of
clk_prepare_enable() (and clk_disable() instead of clk_unprepare_disable()).
Signed-off-by: Paul Osmialowski <p.osmialowsk@...sung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
drivers/i2c/busses/i2c-s3c2410.c | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index e828a1dba0e5..8bfd5234d305 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -782,14 +782,16 @@ static int s3c24xx_i2c_xfer(struct i2c_adapter *adap,
int ret;
pm_runtime_get_sync(&adap->dev);
- clk_prepare_enable(i2c->clk);
+ ret = clk_enable(i2c->clk);
+ if (ret)
+ return ret;
for (retry = 0; retry < adap->retries; retry++) {
ret = s3c24xx_i2c_doxfer(i2c, msgs, num);
if (ret != -EAGAIN) {
- clk_disable_unprepare(i2c->clk);
+ clk_disable(i2c->clk);
pm_runtime_put(&adap->dev);
return ret;
}
@@ -799,7 +801,7 @@ static int s3c24xx_i2c_xfer(struct i2c_adapter *adap,
udelay(100);
}
- clk_disable_unprepare(i2c->clk);
+ clk_disable(i2c->clk);
pm_runtime_put(&adap->dev);
return -EREMOTEIO;
}
@@ -1178,7 +1180,7 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
clk_prepare_enable(i2c->clk);
ret = s3c24xx_i2c_init(i2c);
- clk_disable_unprepare(i2c->clk);
+ clk_disable(i2c->clk);
if (ret != 0) {
dev_err(&pdev->dev, "I2C controller init failed\n");
return ret;
@@ -1191,6 +1193,7 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
i2c->irq = ret = platform_get_irq(pdev, 0);
if (ret <= 0) {
dev_err(&pdev->dev, "cannot find IRQ\n");
+ clk_unprepare(i2c->clk);
return ret;
}
@@ -1199,6 +1202,7 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
if (ret != 0) {
dev_err(&pdev->dev, "cannot claim IRQ %d\n", i2c->irq);
+ clk_unprepare(i2c->clk);
return ret;
}
}
@@ -1206,6 +1210,7 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
ret = s3c24xx_i2c_register_cpufreq(i2c);
if (ret < 0) {
dev_err(&pdev->dev, "failed to register cpufreq notifier\n");
+ clk_unprepare(i2c->clk);
return ret;
}
@@ -1222,6 +1227,7 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
if (ret < 0) {
dev_err(&pdev->dev, "failed to add bus to i2c core\n");
s3c24xx_i2c_deregister_cpufreq(i2c);
+ clk_unprepare(i2c->clk);
return ret;
}
@@ -1243,6 +1249,8 @@ static int s3c24xx_i2c_remove(struct platform_device *pdev)
{
struct s3c24xx_i2c *i2c = platform_get_drvdata(pdev);
+ clk_unprepare(i2c->clk);
+
pm_runtime_disable(&i2c->adap.dev);
pm_runtime_disable(&pdev->dev);
@@ -1271,10 +1279,13 @@ static int s3c24xx_i2c_resume(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct s3c24xx_i2c *i2c = platform_get_drvdata(pdev);
+ int ret;
- clk_prepare_enable(i2c->clk);
+ ret = clk_enable(i2c->clk);
+ if (ret)
+ return ret;
s3c24xx_i2c_init(i2c);
- clk_disable_unprepare(i2c->clk);
+ clk_disable(i2c->clk);
i2c->suspended = 0;
return 0;
--
2.1.4
--
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/
Powered by blists - more mailing lists