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Mon, 29 Sep 2025 09:27:29 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id yposIAFR2mh0SAAAD6G6ig (envelope-from ); Mon, 29 Sep 2025 09:27:29 +0000 Date: Mon, 29 Sep 2025 11:27:27 +0200 From: Oscar Salvador To: Yang Shi Cc: muchun.song@linux.dev, david@redhat.com, akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, carl@os.amperecomputing.com, cl@gentwo.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: hugetlb: avoid soft lockup when mprotect with PROT_MTE Message-ID: References: <20250926162034.1785899-1-yang@os.amperecomputing.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250926162034.1785899-1-yang@os.amperecomputing.com> X-Rspamd-Action: no action X-Stat-Signature: 76pfsykn15q4dwybwwwsat11rss6ty4o X-Rspamd-Queue-Id: 3DD4F1A0002 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1759138051-337882 X-HE-Meta: U2FsdGVkX1+TS9ycGmAlzRjGGoKW2tlw9eWLwdzHWutFKY4zKXfa5h2Ragt2I3HnGAzrWdZa0QGPjOyOssgtfYlkN+Nzqjzl9f/ZIe0Fy5nltDFMVFmyG5nCvWJbaETrb/0S3mZS9WVGb1PZ0TIVv+7/JCUhLCcalhK7TjxzJnqowChb5qmomsgZWnysRxw6PZQmaHaHyiA+SOCOTiIKg5EAEjU1r21h9gEaj/fq5AoPdQxGFH8SgjMjSweQwIqP/4cjWcpq0nfs39VwMOLrOFi8wrHoKp2HhRpX2XH6v/gljP2rEen/1NAR9nVqWRyW6bbz089Bw0g76t/RtfwgXMKSpgPj6AYtcc6heTLXf+FOFhs1eLyPepG0jZZHPDAcz12j1PbZS5lfOPQu2sR74ux4r+p3c3D2y5De7oKOLxM8PPetqPLtALpw7pZG/U/jeHj21ILSXaZ9lazFMLukcrjTPEhiMYwV0t8GksO0v2Tv6aYezNBtR3oJCmPER3zZNorNk2oCOC4genpdhWjRTlP2Px4SzWsxfn0a7DJs8k27SKMNC/QkcKqtWgzVtnUOUW4zGRRupt1KY+yjctDHeeIKGMlyJC+2F+vUshM2gPE0Imta0KToV3aQFnqCY3kNzARJWhU36XxWbGBACZCMeyEvDhxzSCOx52RvaVVCdofr9u/yh7MmyFal/tXgxX5iKhzLG89bATr8OaXp6a3fJjFT70zZOBixrd+TaTjXl09eTqt+jHSEl6mTce9/mxnwoLu/WhLzPBo3gRChB6TyVl+TtldzI3kuBfHA8qW5Kf788rjslY3u5UELxVV8HiKIwHmQuABXamBMVH2l4z0PL/J18gv47dIGp8436CoB0q5LHR+j1d7NPHfBgv0zpI3kpdf2NwyFIScuKEi3P9whvruJl7YtxKaXPvixMowJE8jOJygXq1xWiV4rBdQ+Re/cxBU4XBn92x3CCWp5OYU kVbX5TQg MDZ6OYbGH8yD25Ib2Xh8GzT2SpcN5/C4iRQLmFTUzEXNs38F+Fg74X6W5GqS3SlH3rre1dj+9l7/KT+miJeFWJ/PBr2Jbryj0yg5yCg1lvgAPSKXLZUHvRa/+WJRchfESU/Am1JUVIJvJjXzlpHaXFtPFsl4cbKXQrx6wGPoYk4TdA443cXQk0eGYrQQzFd5x8hJo3XHtomw05Qifyd5yfGjKn9aSgp9o9PnQPnfMoB7AnXloISpp/JT5I6H2+CSuSiZqpCafOLsz4GveF10D/7ncrffoNJ4zi6VMTUV8y98gP2h5ri8gF9akkpQC5Xd+lp6Xh67SSx4W3JqLDFmAFNpXONF3QyhG3U62xRCoFS/etIpI+jl/wb/JusPJMAiYiaLxe5yMeZaasXMFE61VuRxw7sQx/GtfKSdU34N2lZBYXclt638gd5Qk7aKvHMrmYB1Q1hRDqKobD9ey59fGR7WEcw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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