Messages in this thread | | | Subject | Re: Is 386 processor still supported? | From | Peter Zijlstra <> | Date | Thu, 08 Jan 2009 15:13:45 +0100 |
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On Thu, 2009-01-08 at 14:05 +0100, Jiri Kosina wrote: > [ CCs added ] > > On Thu, 8 Jan 2009, Adam Osuchowski wrote: > > > Recently, I found such piece of code in kernel 2.6.28 compiled for 386 > > processor: > > > > # grep M386 .config > > CONFIG_M386=y > > # objdump -d vmlinux | grep -A11 '<_spin_lock>:' > > c0321827 <_spin_lock>: > > c0321827: 89 e2 mov %esp,%edx > > c0321829: 81 e2 00 f0 ff ff and $0xfffff000,%edx > > c032182f: ff 42 14 incl 0x14(%edx) > > c0321832: ba 00 01 00 00 mov $0x100,%edx > > c0321837: f0 66 0f c1 10 lock xadd %dx,(%eax) > > c032183c: 38 f2 cmp %dh,%dl > > c032183e: 74 06 je c0321846 <_spin_lock+0x1f> > > c0321840: f3 90 pause > > c0321842: 8a 10 mov (%eax),%dl > > c0321844: eb f6 jmp c032183c <_spin_lock+0x15> > > c0321846: c3 ret > > > > But there is no xadd instruction on 386 processors. It is available on > > 486+ only. I have no chance to run this kernel on real 386 box, so I can't > > check it in practice, but I think it will not run. > > > > It is not compiler problem because it is explicitly written in assembly > > in __raw_spin_lock() function (include/asm-x86/spinlock.h) and there is > > no alternative code depending on CONFIG_M386. > > Hmm, this really looks like a bug to me. How about something like this > (untested). > > > From: Jiri Kosina <jkosina@suse.cz> > Subject: x86: make spinlocks available on machines without xadd insn > > Current kernel wouldn't compile on ancient x86 machines that don't support > xadd instruction, as ticket spinlocks implementation unconditionally uses > it. > > On machines without CONFIG_X86_XADD, use old-style byte spinlock > implementation instead.
afaik we don't support i386-smp and up spinlocks are trivial preempt_disable() calls.
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