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SubjectRe: shm in 2.1.125
On 10 Oct 1998, Christoph Rohland wrote:

>Unfortunately the changes for 2.1.125 did extend the maximum possible
>SHM segment size from (128M - 1 page) to 128M and make a misconfigured
>kernel behave very bad!
>
>since shm_npages in shmid_ds is unsigned short we can at most allocate
>65535 pages. This is not noted by shmget which happily gives you a
>segment for e.g. 256M = 65536 pages. But the following shmat will see
>0 pages for the segment and the application will get nothing (but a
>seg-fault ;-). Worse: on deletion the total count for shm pages will
>be decreased by also 0. So following allocations fail after a while.

Maybe that explains why my EGCS 1.1 started seg faulting left and right
with 2.1.125. Doug Ledford's "diff test" found nothing amiss (500 runs,
two days), nor had my previous "make kernel repeatedly" tests (300 runs,
two days) under previous kernels.

I was getting really worried when a 'make -j20' under the 2.1.125 kernel
resulted in 5 of the EGCS's seg faulting.

-George


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