Messages in this thread |  | | | Date | Tue, 3 May 2005 21:13:37 -0400 (EDT) | | From | Jason Baron <> | | Subject | Re: [PATCH] tty races |
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On Tue, 3 May 2005, Andrew Morton wrote:
> > > We want to move away from lock_kernel()-based locking. > > > > > > > I completely agree, but unfortunately lock_kernel() is currently used > > extensively throughout the tty layer. > > Well no - it's being migrated over to use tty_sem. We shouldn't start > heading in the reverse direction. Plus your patch reverts part of > http://linux.bkbits.net:8080/linux-2.5/diffs/drivers/char/tty_io.c@1.156?nav=index.html|src/|src/drivers|src/drivers/char|hist/drivers/char/tty_io.c > in ways which might be unsafe. >
The patch I proposed does not add any lock_kernel() based locking. The only locking it adds is more tty_sem based locking to cover the driver->open() method. I agree though that it relies on the BKL for correctness.
Indeed, that is precisely that patch which introduced the problems I've pointed out.
> > lock_kernel() is used extensively throughout the tty layer. We can > > re-write the locking for the layer, but I'd like to see this bug fix in > > 2.6.12, if that isn't done in time. > > Sorry, but AFAICT all you have done is to advocate for the existing patch > without having attempted to fix this problem with tty_sem. Please try to > come up with a tty_sem-based fix. >
The patch I proposed fixes the open vs. open race using the tty_sem. The open vs. close race is closed by removing locking. Less locking seems better to me.
If you're still not happy, I'll wrap the close path in the tty_sem...
thanks,
-Jason
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