On Monday August 3, maan@xxxxxxxxxxxxxxx wrote: > On 15:06, Neil Brown wrote: > > > Here is a revised patch that puts calls to the new functions into > > > the ->hot_*_disk methods as you propose. > > > > Thanks. Much better. > > Calling md_integrity_check from the ->error routines isn't a good idea > > though. They can be called in interrupt context, and > > md_integrity_check can call kmalloc(..., GFP_KERNEL) which might try > > to sleep. That would be bad. > > We don't need the call in ->error, having it in ->hot_remove_disk is > > adequate, as that is called soon after any failure (it doesn't wait > > for the sysadmin to "mdadm --remove ...".). > > > > So I have made that change and updated the comment accordingly. > > Thanks. Sorry if this is a FAQ, but how can one tell whether a given > function may be called in interrupt context? Is there a better way > than recursively checking all its callers? I think you just have to 'know'. :-( Some functions which mustn't be called from interrupts are 'documented' as such by calling "might_sleep()", but there is no similar documentation for the reverse. All ->bi_endio routines are called from interrupts.. or maybe from softirqs or something similar. I think the important point is that they are called without a process context, so they cannot sleep (i.e. no kmalloc unless you use GFP_ATOMIC, no mutex_lock, no wait_event etc) and should use spin_lock_irqsave or spin_lock_bh rather than a bare spin_lock. NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
