Re: [9fans] paging

[Alexander Viro <viro@math.psu.edu>]

On Mon, 8 Jan 2001 forsyth@caldo.demon.co.uk wrote:

> - it can happen with paging to local disc
> - it CAN happen when paging over an ethernet to a file from a file server
> - it can lead to process hangs or traps; rio and acme are common targets
> - to judge from last-write times on the paging files, the problem is caused by paging
> - uniprocessors are affected
> - we most easily provoke it using charon to read huge pages on slashdot(!)
> - rio and acme (and emu) use rfork(RFMEM).  coincidence?
> - it did not happen with 2nd edition on any platform
> 
> at one point it seemed that it might be related to shared text/memory, because
> it once left a particular program corrupted but enough elsewhere was
> running that we could look at it (normally it damages enough of the interface
> that it is hard to debug).  i'm still not convinced.

	Just a gut feeling: procflushseg() and stuff triggered by it.
Check for situations when process gets created in the middle of procflushseg().
I didn't look deep enough, but it just screams "races will grow here, even
if there is none right now"...