Re: Unserializing ioctl() system calls

[viro]

On Fri, May 21, 2004 at 10:46:45PM -0400, Spinka, Kristofer wrote:
> 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.
> 
> 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.
> 
> The default behavior would adhere to existing standards, 
> and if the flag is present (in the underlying module), we 
> let the module (or modules) handle it.
> 
> Reasonable?

No.  Flags on drivers are never a good idea.  What's more, if somebody
wants that shit parallelized they can always drop BKL upon entry and
reacquire on exit from their ->ioctl().
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