Messages in this thread |  | | From | "Bao C. Ha" <> | Subject | RE: Different old_mmap behavior between 2.4.5 and 2.4.8 | Date | Tue, 11 Sep 2001 11:31:22 -0700 |
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> On Mon, Sep 10, 2001 at 06:30:55PM -0700, Bao C. Ha wrote: > > Is this supposed to be the correct behavior? What changes > > make the newer kernels to return different pointers? We > > are running on the sh4 architecture but I think these calls > > come from malloc() which should be arch-independent. > > The result from earlier kernels is wrong. If your code > requires that the same address is returned as was specified > then you need to pass in the MAP_FIXED flag.
Unfortunately, it is the linuxthreads code that is broken on the sh4 platform. It seems that the pointers are moved due to cache aliasing. I am trying to raise awareness that this is breaking pthreads applications on sh4-linux.
Following is the relevant segment of linuxthreads that is broken:
In function pthread_allocate_stack(), file manager.c: ....... # ifdef _STACK_GROWS_DOWN new_thread = default_new_thread; new_thread_bottom = (char *) (new_thread + 1) - stacksize; map_addr = new_thread_bottom - guardsize; res_addr = mmap(map_addr, stacksize + guardsize, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (res_addr != map_addr) { /* Bad luck, this segment is already mapped. */ if (res_addr != MAP_FAILED) munmap (res_addr, stacksize + guardsize); return -1; } .......
We resort to patching the MAP_FIXED back to linuxthreads until we get a resolution on this problem.
Thanks. Bao
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