Re: [patch] updates for the pipe code

From: Richard Gooch (rgooch@atnf.csiro.au)
Date: Fri Mar 03 2000 - 16:21:26 EST


Manfred Spraul writes:
> The last patch contained a race: if 2 threads read and write to a pipe
> concurrently, then wake-up's could get lost. I forgot to check PIPE_LEN
> after I reacquired PIPE_LOCK.

Hm. This is a problem with your patch, right? What about the problem I
reported back on 16-FEB? It's still happening with 2.3.48. The problem
does not occur with 2.2.14.

> Hi, all. I've been noticing odd behaviour with named pipes under
> recent 2.3.x kernels (at least since 2.3.36 and possibly before).
>
> If you open a FIFO with O_RDONLY and then call read(2), and then
> another process writes to the FIFO, the read(2) call doesn't return. A
> subsequent writer process does wake up the reader, however.
>
> Has anybody else noticed this behaviour?

I've noticed this problem on UP and SMP systems. It doesn't always
happen, but it *does* happen :-(

                                Regards,

                                        Richard....
Permanent: rgooch@atnf.csiro.au
Current: rgooch@ras.ucalgary.ca

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