From: Viresh Kumar <viresh.kumar@linaro.org>
To: Stephen Boyd <sboyd@codeaurora.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
nm@ti.com
Subject: Re: [PATCH 04/17] PM / OPP: Introduce dev_pm_opp_get_max_volt_latency()
Date: Wed, 13 Jan 2016 11:04:47 +0530 [thread overview]
Message-ID: <20160113053447.GB6050@ubuntu> (raw)
In-Reply-To: <20160112194537.GZ22188@codeaurora.org>
On 12-01-16, 11:45, Stephen Boyd wrote:
> > + * Locking: This function takes rcu_read_lock().
>
> False.
Yeah, I realized it and fixed it right after sending it:
+ * Locking: This function internally uses mutex locks to keep the integrity of
+ * the internal data structures. Callers should ensure that this function is
+ * *NOT* called under RCU protection or in contexts where mutex cannot be
+ * locked.
> > + /*
> > + * Hold our list modification lock here as regulator_set_voltage_time()
> > + * can possibly take another mutex, which isn't allowed within rcu
> > + * locks.
> > + */
> > + mutex_lock(&dev_opp_list_lock);
>
> So now we take the list modification mutex. Why can't we
> rcu_read_lock(), find the min and max voltage, and then release
> the read lock and ask regulator framework for the voltage time?
That was possible before this series came in..
> From what I can tell we're just trying to make sure that the list
> is stable when iterating through it to find the min/max voltage.
Hmm, we have pointer to regulator within the dev-opp struct. If we
drop the lock, the dev-opp struct can get freed and regulator will be
put just before that. So, we may be using an already freed resource.
How do you suggest we fix it ?
--
viresh
next prev parent reply other threads:[~2016-01-13 5:34 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-22 10:16 [PATCH 00/17] PM / OPP: Introduce APIs to transition OPPs Viresh Kumar
2015-12-22 10:16 ` [PATCH 01/17] PM / OPP: get/put regulators from OPP core Viresh Kumar
2016-01-11 23:21 ` Stephen Boyd
2016-01-12 3:05 ` Viresh Kumar
2016-01-12 5:23 ` Viresh Kumar
2016-01-12 19:32 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 02/17] PM / OPP: Add APIs to set regulator-name Viresh Kumar
2016-01-12 1:18 ` Stephen Boyd
2016-01-12 4:43 ` Viresh Kumar
2015-12-22 10:16 ` [PATCH 03/17] PM / OPP: Disable OPPs that aren't supported by the regulator Viresh Kumar
2016-01-12 1:19 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 04/17] PM / OPP: Introduce dev_pm_opp_get_max_volt_latency() Viresh Kumar
2016-01-12 1:25 ` Stephen Boyd
2016-01-12 5:10 ` Viresh Kumar
2016-01-12 19:45 ` Stephen Boyd
2016-01-13 5:34 ` Viresh Kumar [this message]
2016-01-18 7:23 ` Viresh Kumar
2016-01-21 0:20 ` Stephen Boyd
2016-01-21 2:32 ` Viresh Kumar
2016-01-21 2:43 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 05/17] PM / OPP: Introduce dev_pm_opp_get_max_transition_latency() Viresh Kumar
2016-01-12 2:20 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 06/17] PM / OPP: Parse clock-latency and voltage-tolerance for v1 bindings Viresh Kumar
2016-01-12 1:29 ` Stephen Boyd
2016-01-12 5:14 ` Viresh Kumar
2016-01-13 0:36 ` Stephen Boyd
2016-01-13 5:35 ` Viresh Kumar
2016-01-15 1:54 ` Stephen Boyd
2016-01-15 1:54 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 07/17] PM / OPP: Manage device clk Viresh Kumar
2016-01-12 1:32 ` Stephen Boyd
2016-01-12 5:43 ` Viresh Kumar
2016-01-12 19:47 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 08/17] PM / OPP: Add dev_pm_opp_set_rate() Viresh Kumar
2016-01-12 1:40 ` Stephen Boyd
2016-01-12 6:58 ` Viresh Kumar
2016-01-13 0:49 ` Stephen Boyd
2016-01-13 5:51 ` Viresh Kumar
2015-12-22 10:16 ` [PATCH 10/17] cpufreq: dt: Rename 'need_update' to 'opp_v1' Viresh Kumar
2016-01-12 1:41 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 11/17] cpufreq: dt: OPP layers handles clock-latency for V1 bindings as well Viresh Kumar
2016-01-12 1:41 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 12/17] cpufreq: dt: Pass regulator name to the OPP core for V1 bindings Viresh Kumar
2016-01-12 1:53 ` Stephen Boyd
2016-01-12 7:11 ` Viresh Kumar
2016-01-13 0:43 ` Stephen Boyd
2016-01-13 5:47 ` Viresh Kumar
2016-01-13 11:15 ` Mark Brown
2015-12-22 10:16 ` [PATCH 13/17] cpufreq: dt: Unsupported OPPs are already disabled Viresh Kumar
2016-01-12 1:53 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 14/17] cpufreq: dt: Reuse dev_pm_opp_get_max_transition_latency() Viresh Kumar
2016-01-12 1:54 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 15/17] cpufreq: dt: Use dev_pm_opp_set_rate() to switch frequency Viresh Kumar
2016-01-12 1:55 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 16/17] cpufreq: dt: drop references to DT node Viresh Kumar
2016-01-12 1:55 ` Stephen Boyd
2015-12-22 10:16 ` [PATCH 17/17] cpufreq: dt: No need to allocate resources anymore Viresh Kumar
2016-01-12 2:20 ` Stephen Boyd
2016-01-12 7:34 ` Viresh Kumar
2016-01-21 1:18 ` Stephen Boyd
2016-01-21 2:36 ` Viresh Kumar
2016-01-21 2:45 ` Stephen Boyd
2016-01-25 10:33 ` Viresh Kumar
2015-12-22 10:20 ` [PATCH 09/17] cpufreq: dt: Convert few pr_debug/err() calls to dev_dbg/err() Viresh Kumar
2016-01-12 1:40 ` Stephen Boyd
2015-12-23 3:12 ` [PATCH 00/17] PM / OPP: Introduce APIs to transition OPPs Rafael J. Wysocki
2015-12-23 2:46 ` Viresh Kumar
2016-01-11 16:28 ` Viresh Kumar
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