| Date | Tue, 21 Oct 2014 08:46:24 +0200 | From | Philippe Rétornaz <> | Subject | Re: [PATCH v2 01/47] kernel: Add support for poweroff handler call chain |
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Hello
[...] > - Use raw notifiers protected by spinlocks instead of atomic notifiers [...]
> +/** > + * do_kernel_power_off - Execute kernel poweroff handler call chain > + * > + * Calls functions registered with register_power_off_handler. > + * > + * Expected to be called from machine_power_off as last step of > + * the poweroff sequence. > + * > + * Powers off the system immediately if a poweroff handler function > + * has been registered. Otherwise does nothing. > + */ > +void do_kernel_power_off(void) > +{ > + spin_lock(&power_off_handler_lock); > + raw_notifier_call_chain(&power_off_handler_list, 0, NULL); > + spin_unlock(&power_off_handler_lock); > +}
I don't get it. You are still in atomic context inside the poweroff callback since you lock it with a spinlock.
It does not change much from the atomic notifier which was doing exactly the same thing but with RCU:
rcu_read_lock(); ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls); rcu_read_unlock();
Why not using the blocking_notifier_* family ? It will lock with a read-write semaphore under which you can sleep.
For instance, twl4030_power_off will sleep, since it is doing I2C access. So you cannot call it in atomic context.
Thanks,
Philippe
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