Gilles Chanteperdrix wrote: > On 8/7/07, Jan Kiszka <[EMAIL PROTECTED]> wrote: >> Gilles Chanteperdrix wrote: >>> Jan Kiszka wrote: >>>> Hi all, >>>> >>>> we are getting a lot of >>>> >>>> BUG: sleeping function called from invalid context at mm/page_alloc.c:1225 >>>> in_atomic():1, irqs_disabled():0 >>>> [<c010305d>] show_trace_log_lvl+0x1a/0x2f >>>> [<c0103156>] show_trace+0x12/0x14 >>>> [<c0103915>] dump_stack+0x16/0x18 >>>> [<c010c4ab>] __might_sleep+0xcd/0xd3 >>>> [<c0149488>] __alloc_pages+0x32/0x281 >>>> [<c014fdd2>] copy_page_range+0x221/0x41e >>>> [<c010ec18>] copy_process+0x9e1/0xfe2 >>>> [<c010f415>] do_fork+0x99/0x176 >>>> [<c0100e75>] sys_clone+0x33/0x39 >>>> [<c0102aaf>] syscall_call+0x7/0xb >>>> ======================= >>>> >>>> here due to a Xenomai program issuing system() calls. >>>> >>>> After once again dissecting the "nice" mm code (sigh...), the reason >>>> turned out to be plain simple: >>>> >>>> copy_pte_range(...); >>>> spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); >>>> copy_one_pte(...); >>>> if (is_cow_mapping(vm_flags)) >>>> alloc_page_vma(GFP_HIGHUSER, ...); >>>> __alloc_pages(...) >>>> might_sleep_if(gfp_mask & __GFP_WAIT); >>>> >>>> And this is true due to #define GFP_HIGHUSER (__GFP_WAIT | ... >>>> >>>> So the bad news is that the COW code in likely all i-pipe versions is >>>> broken. But the good new is that this might be easily fixable by >>>> providing the right gfp_mask. GFP_ATOMIC? >>> It does not look like a good solution, you are going to empty the >>> GFP_ATOMIC pools. The proper solution would rather be to look at the >>> real mm code (I mean not the one I wrote) and see how they cope with >>> this issue. >> Mmpf. What are the chances for a quick fix within the next days? We have >> to consider alternatives right now here because the whole system is >> meant for production purpose next week (C-ELROB '07). >> >> OK, I'm already finding myself inside the code :-/. What about this >> approach: We try to alloc with GFP_ATOMIC. Once this fails, we break >> out, drop all locks (just like it happens in case of need_resched()), >> try to fill up the pool, and restart then. What would reliably make >> Linux refill its atomic pool? >> >> Alternative approach: preallocate the required pages before entering the >> loop in copy_pte_range. But that may require more code changes. > > I would say the real fix is to drop momentarily the spinlock(s?) for > allocating. >
Are you sure it's safe to drop locks in the (logical) middle of copy_one_pte()? I can't tell yet from the few glances I took. It's just my feeling that says "no" so far. Jan
signature.asc
Description: OpenPGP digital signature
_______________________________________________ Adeos-main mailing list [email protected] https://mail.gna.org/listinfo/adeos-main
