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?
Jan
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