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DKIM_TRACE(0.00)[suse.de:+] X-Spam-Score: -4.51 On Fri, Sep 26, 2025 at 09:20:34AM -0700, Yang Shi wrote: > When calling mprotect() with PROT_MTE, kernel will initialize MTE tags > for every single page in the affected area. Soft lockup was observed > when doing this for large HugeTLB memory area in our customer's workload > (~300GB memory): > > watchdog: BUG: soft lockup - CPU#98 stuck for 23s! [t2_new_sysv:126916] > > CPU: 98 PID: 126916 Comm: t2_new_sysv Kdump: loaded Not tainted 6.17-rc7 > Hardware name: GIGACOMPUTING R2A3-T40-AAV1/Jefferson CIO, BIOS 5.4.4.1 07/15/2025 > pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : mte_clear_page_tags+0x14/0x24 > lr : mte_sync_tags+0x1c0/0x240 > sp : ffff80003150bb80 > x29: ffff80003150bb80 x28: ffff00739e9705a8 x27: 0000ffd2d6a00000 > x26: 0000ff8e4bc00000 x25: 00e80046cde00f45 x24: 0000000000022458 > x23: 0000000000000000 x22: 0000000000000004 x21: 000000011b380000 > x20: ffff000000000000 x19: 000000011b379f40 x18: 0000000000000000 > x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 > x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 > x11: 0000000000000000 x10: 0000000000000000 x9 : ffffc875e0aa5e2c > x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000 > x5 : fffffc01ce7a5c00 x4 : 00000000046cde00 x3 : fffffc0000000000 > x2 : 0000000000000004 x1 : 0000000000000040 x0 : ffff0046cde7c000 > > Call trace: >   mte_clear_page_tags+0x14/0x24 >   set_huge_pte_at+0x25c/0x280 >   hugetlb_change_protection+0x220/0x430 >   change_protection+0x5c/0x8c >   mprotect_fixup+0x10c/0x294 >   do_mprotect_pkey.constprop.0+0x2e0/0x3d4 >   __arm64_sys_mprotect+0x24/0x44 >   invoke_syscall+0x50/0x160 >   el0_svc_common+0x48/0x144 >   do_el0_svc+0x30/0xe0 >   el0_svc+0x30/0xf0 >   el0t_64_sync_handler+0xc4/0x148 >   el0t_64_sync+0x1a4/0x1a8 > > Soft lockup is not triggered with THP or base page because there is > cond_resched() called for each PMD size. > > So add cond_resched() for hugetlb to avoid soft lockup. > > Fixes: 25c17c4b55de ("hugetlb: arm64: add mte support") > Tested-by: Carl Worth > Signed-off-by: Yang Shi Acked-by: Oscar Salvador > --- > mm/hugetlb.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index cb5c4e79e0b8..fe6606d91b31 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -7242,6 +7242,8 @@ long hugetlb_change_protection(struct vm_area_struct *vma, > psize); > } > spin_unlock(ptl); > + > + cond_resched(); > } > /* > * Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare > -- > 2.47.0 > -- Oscar Salvador SUSE Labs