Re: Unserializing ioctl() system calls

[Andi Kleen]

"Spinka, Kristofer" <kspinka@xxxxxxxxx> writes:

> I noticed that even in the 2.6.6 code, callers to ioctl system call
> (sys_ioctl in fs/ioctl.c) are serialized with {lock,unlock}_kernel().
>
> I realize that many kernel modules, and POSIX for that matter, may not
> be ready to make this more concurrent.

POSIX doesn't care how the kernel implements locking.

> I propose adding a flag to indicate that the underlying module would
> like to support its own concurrency management, and thus we avoid
> grabbing the BKL around the f_op->ioctl call.

Better would be probably a unlocked_ioctl() entry point in f_op. Should
be pretty easy to implement.

There is also the additional issue that on 64bit systems with 32bit
userland the ioctl emulation currently relies on the BKL.

-Andi

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