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Message-ID: <CAJZ5v0j=rLMNOspVSub7MZ4PxrMoo5kao_B226-Lx4UjPb4wCw@mail.gmail.com> Date: Mon, 27 Jul 2015 14:39:14 +0200 From: "Rafael J. Wysocki" <rafael@...nel.org> To: Viresh Kumar <viresh.kumar@...aro.org>, Russell King <linux@....linux.org.uk> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM list <linux-pm@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v3] cpufreq: Avoid attempts to create duplicate symbolic links On Mon, Jul 27, 2015 at 4:29 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote: > On 26-07-15, 02:28, Rafael J. Wysocki wrote: >> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com> >> >> After commit 87549141d516 (cpufreq: Stop migrating sysfs files on >> hotplug) there is a problem with CPUs that share cpufreq policy >> objects with other CPUs and are initially offline. >> >> Say CPU1 shares a policy with CPU0 which is online and is registered >> first. As part of the registration process, cpufreq_add_dev() is >> called for it. It creates the policy object and a symbolic link >> to it from the CPU1's sysfs directory. If CPU1 is registered >> subsequently and it is offline at that time, cpufreq_add_dev() will >> attempt to create a symbolic link to the policy object for it, but >> that link is present already, so a warning about that will be >> triggered. >> >> To avoid that warning, make cpufreq use an additional CPU mask >> containing related CPUs that are actually present for each policy >> object. That mask is initialized when the policy object is populated >> after its creation (for the first online CPU using it) and it includes >> CPUs from the "policy CPUs" mask returned by the cpufreq driver's >> ->init() callback that are physically present at that time. Symbolic >> links to the policy are created only for the CPUs in that mask. >> >> If cpufreq_add_dev() is invoked for an offline CPU, it checks the >> new mask and only creates the symlink if the CPU was not in it (the >> CPU is added to the mask at the same time). >> >> In turn, cpufreq_remove_dev() drops the given CPU from the new mask, >> removes its symlink to the policy object and returns, unless it is >> the CPU owning the policy object. In that case, the policy object >> is moved to a new CPU's sysfs directory or deleted if the CPU being >> removed was the last user of the policy. >> >> While at it, notice that cpufreq_remove_dev() can't fail, because >> its return value is ignored, so make it ignore return values from >> __cpufreq_remove_dev_prepare() and __cpufreq_remove_dev_finish() >> and prevent these functions from aborting on errors returned by >> __cpufreq_governor(). Also drop the now unused sif argument from >> them. >> >> Fixes: 87549141d516 (cpufreq: Stop migrating sysfs files on hotplug) >> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> >> Reported-by: Russell King <linux@....linux.org.uk> >> --- >> >> This goes back to the https://patchwork.kernel.org/patch/6856011/ >> idea, but has a couple of bugs fixed and goes a it further with >> cleaning things up. >> >> --- >> drivers/cpufreq/cpufreq.c | 108 +++++++++++++++++++++++----------------------- >> include/linux/cpufreq.h | 1 >> 2 files changed, 56 insertions(+), 53 deletions(-) > > Acked-by: Viresh Kumar <viresh.kumar@...aro.org> Thanks! Russell, can you test this one, please? Rafael -- 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/
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