On 2 August 2013 12:08, Mike Turquette mturquette@linaro.org wrote:
Quoting Viresh Kumar (2013-08-01 22:02:37)
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On Thu, Aug 1, 2013 at 6:08 PM, Michael Giardino giardino@ece.gatech.edu wrote:
Hi,
I hope this is the right spot to ask this.
Is there any way to change the cpu frequency using the cpufreq driver from within an hrtimer callback function? I encounter a kernel panic at cpufreq.c line 255 (260 in 3.9.5)
It is not just about the notifiers.
Performing a clock rate change and voltage regulator transition (DVFS) is not a short operation on many ARM platforms. Relocking a PLL and waiting for a regulator to step and stabilize can take well over 100 milliseconds and some of those functions might sleep.
BTW, The routine in question doesn't change frequency by itself. But the caller of this routine will change clk just after/before calling this routine.
I don't really know why this code was initially written there, but I don't think we should add such a BUG() or WARN() to satisfy performance of a system.
They should be used only when it is not possible to execute the notifier when interrupts are disabled.
You have any clue why this code was placed here?