Re: [PATCH] x86, efi: Don't recursively acquire rtc_lock

From: Jan Beulich
Date: Wed Aug 03 2011 - 22:53:45 EST


>>> Matt Fleming 08/03/11 11:04 PM >>>
>From: Matt Fleming
>
>A deadlock was introduced on x86 in commit ef68c8f87ed1 ("x86:
>Serialize EFI time accesses on rtc_lock") because efi_get_time() and
>friends can be called with rtc_lock already held by
>read_persistent_time(), e.g.
>
>timekeeping_init()
>read_persistent_clock() <-- acquire rtc_lock
>efi_get_time()
>phys_efi_get_time() <-- acquire rtc_lock
>
>Move the locking up into the caller of efi.get_time() and provide some
>wrappers for use in other parts of the kernel instead of calling
>efi.get_time(), etc directly. This way we can hide the rtc_lock dance
>inside of arch/x86.

Seems the wrong approach to me: The call happening with the lock held
is the wrong part imo, and hence the fix ought to be to drop the lock
there.

Jan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/