Date: Thu, 20 Dec 2001 14:26:24 -0800 (PST) From: Julian Elischer <julian@elischer.org> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: John Baldwin <jhb@FreeBSD.org>, arch@FreeBSD.org, Alfred Perlstein <bright@mu.org> Subject: Re: Kernel stack size and stacking: do we have a problem ? Message-ID: <Pine.BSF.4.21.0112201412310.46573-100000@InterJet.elischer.org> In-Reply-To: <3954.1008885976@critter.freebsd.dk>
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On Thu, 20 Dec 2001, Poul-Henning Kamp wrote: > > A) We should probably implement > int enough_stack() a full unoptimised but correct version would be: int enough_stack(u_int needed) { caddr_t addr, addr2; if needed > KSTACK_PAGES * PAGESIZE return 0; /* catch stupid values */ addr1 = &needed; addr2 = (caddr_t)curthread->td_kstack + needed; return (addr1 > addr2) } > and apply it in some strategic places so we can fail gracely > rather than panic when we run out of kernel stack. > > B) We have no idea how to sanely fix VOP_ since it is synchronous. > When I say "sanely" I'm referring to the fact that the VOP > code is scary enough as it is and we don't want to make it even > hairier, lest we loose the few filesystem hackers we have, not > to mention the fact that we would probably never complete the > conversion in the first place (see sys/vnode.h::IS_LOCKING_VFS() > for precedent.) > > C) Variant size kernel stacks are probably not worth the bother, > but sysctl variable kernel stacks might be a good investment. > > C) Netgraph and Geom will use scheduling, possibly with a direct > call optimization to avoid the issue. > Julian hybrid scheme could possibly be adapted to Geom, if it > can be made to maintain ordering (think: softupdates). it does.. > > Thanks for your input gentlemen. The netgraph locking/queueing is an integrated set of code that does both functions. The queing is part and parcel of the locking. it wouldn't work if it were not an async system. > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > phk@FreeBSD.ORG | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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