Greetings, and thanks foro looking into this! Witold Baryluk <baryluk@xxxxxxxxxxxxxxxx> writes: > On 05-03 09:19, Camm Maguire wrote: >> Greetings! The build succeeded, which, alas, means the failure at >> >> http://buildd.debian-ports.org/status/fetch.php?pkg=axiom&arch=alpha&ver=20120301-3&stamp=1335722507 >> >> is again unreproducible, like the kfree_amd64 and ppc examples. Sigh. >> Are there known differences in the cpu cache clearing instructions >> between imago and your machine? >> >> In any case, can one upload by hand builds to debian-ports like one can >> into the official repository? >> >> Take care, >> -- >> Camm Maguire camm@xxxxxxxxxxxxxxxxx >> ========================================================================== >> "The earth is but one country, and mankind its citizens." -- Baha'u'llah > > After lots of investigation, it looks that imb (I-cache memory barrier, > used for flushing instruction cache on single cpu), is not emited or > called when doing __builtin___clear_cache! > > It shouldn't be hard to add, for example using (define_expand > "clear_cache" ... in gcc/config/alpha/alpha.md in gcc, or in libgcc/config/alpha/linux.h > as #define CLEAR_INSN_CACHE(beg, end) ... > > Either of them should just emit, "call_pal 0x86". It is better than > "imb" because imb is not implemented in Tru64 assembler, and better than > "call_pal pal_imb", because pal_imb (which is equal 134), requires > include <pal.h>. > > Beyond that it would be naccassary to update kernel, to detect that user > code called imb, by checking if proper flag in HWPCB structure is set, > and call smp_imb() if naccassary on multi-processor system (probably > when rescheduling this process on different cpu) and clear hwpcb flag, > becuause imb invalidated Icache only on running cpu. > > > Build of axiom package successed on my machine probably by luck, and by > the fact it is single CPU machine with smaller cache than imago (and > older subarchitecture, thus probably less agressive caching). > > What alpha maintainers thinks? Pending a true fix, here is the gcl situation when built on alpha: checking for main in -lX11... yes checking for xdr_double... yes checking __builtin___clear_cache... yes and the relvant gcl code: #define PAL_imb 134 #define imb() \ __asm__ __volatile__ ("call_pal %0 #imb" : : "i" (PAL_imb) : "memory") #define CLEAR_CACHE imb() #ifdef HAVE_BUILTIN_CLEAR_CACHE static int clear_protect_memory(object memory) { void *p,*pe; int i; p=(void *)((unsigned long)memory->cfd.cfd_start & ~(PAGESIZE-1)); pe=(void *)((unsigned long)(memory->cfd.cfd_start+memory->cfd.cfd_size) & ~(PAGESIZE-1)) + PAGESIZE-1; i=mprotect(p,pe-p,PROT_READ|PROT_WRITE|PROT_EXEC); __builtin___clear_cache((void *)memory->cfd.cfd_start,(void *)memory->cfd.cfd_start+memory->cfd.cfd_size); return i; } #endif .... #ifdef HAVE_BUILTIN_CLEAR_CACHE massert(!clear_protect_memory(memory)); #else #ifdef CLEAR_CACHE CLEAR_CACHE; #endif #endif The goal was to exercise the very helpful gcc __builtin___clear_cache support, and to avoid having to maintain our own assembler for all the different cpus in this regard. Clearly, it is easy to revert this on a per architecture basis if absolutely necessary. If gcc does or does not plan on fixing this, please let me know so gcl can adjust as needed. Take care, -- Camm Maguire camm@xxxxxxxxxxxxxxxxx ========================================================================== "The earth is but one country, and mankind its citizens." -- Baha'u'llah -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
