This is a note to let you know that I've just added the patch titled
mm/mprotect: add a cond_resched() inside change_pmd_range()
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: mm-mprotect-add-a-cond_resched-inside-change_pmd_range.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 4991c09c7c812dba13ea9be79a68b4565bb1fa4e Mon Sep 17 00:00:00 2001
From: Anshuman Khandual khandual@linux.vnet.ibm.com Date: Thu, 4 Jan 2018 16:17:52 -0800 Subject: mm/mprotect: add a cond_resched() inside change_pmd_range()
From: Anshuman Khandual khandual@linux.vnet.ibm.com
commit 4991c09c7c812dba13ea9be79a68b4565bb1fa4e upstream.
While testing on a large CPU system, detected the following RCU stall many times over the span of the workload. This problem is solved by adding a cond_resched() in the change_pmd_range() function.
INFO: rcu_sched detected stalls on CPUs/tasks: 154-....: (670 ticks this GP) idle=022/140000000000000/0 softirq=2825/2825 fqs=612 (detected by 955, t=6002 jiffies, g=4486, c=4485, q=90864) Sending NMI from CPU 955 to CPUs 154: NMI backtrace for cpu 154 CPU: 154 PID: 147071 Comm: workload Not tainted 4.15.0-rc3+ #3 NIP: c0000000000b3f64 LR: c0000000000b33d4 CTR: 000000000000aa18 REGS: 00000000a4b0fb44 TRAP: 0501 Not tainted (4.15.0-rc3+) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 22422082 XER: 00000000 CFAR: 00000000006cf8f0 SOFTE: 1 GPR00: 0010000000000000 c00003ef9b1cb8c0 c0000000010cc600 0000000000000000 GPR04: 8e0000018c32b200 40017b3858fd6e00 8e0000018c32b208 40017b3858fd6e00 GPR08: 8e0000018c32b210 40017b3858fd6e00 8e0000018c32b218 40017b3858fd6e00 GPR12: ffffffffffffffff c00000000fb25100 NIP [c0000000000b3f64] plpar_hcall9+0x44/0x7c LR [c0000000000b33d4] pSeries_lpar_flush_hash_range+0x384/0x420 Call Trace: flush_hash_range+0x48/0x100 __flush_tlb_pending+0x44/0xd0 hpte_need_flush+0x408/0x470 change_protection_range+0xaac/0xf10 change_prot_numa+0x30/0xb0 task_numa_work+0x2d0/0x3e0 task_work_run+0x130/0x190 do_notify_resume+0x118/0x120 ret_from_except_lite+0x70/0x74 Instruction dump: 60000000 f8810028 7ca42b78 7cc53378 7ce63b78 7d074378 7d284b78 7d495378 e9410060 e9610068 e9810070 44000022 <7d806378> e9810028 f88c0000 f8ac0008
Link: http://lkml.kernel.org/r/20171214140551.5794-1-khandual@linux.vnet.ibm.com Signed-off-by: Anshuman Khandual khandual@linux.vnet.ibm.com Suggested-by: Nicholas Piggin npiggin@gmail.com Acked-by: Michal Hocko mhocko@suse.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/mprotect.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -166,7 +166,7 @@ static inline unsigned long change_pmd_r next = pmd_addr_end(addr, end); if (!is_swap_pmd(*pmd) && !pmd_trans_huge(*pmd) && !pmd_devmap(*pmd) && pmd_none_or_clear_bad(pmd)) - continue; + goto next;
/* invoke the mmu notifier if the pmd is populated */ if (!mni_start) { @@ -188,7 +188,7 @@ static inline unsigned long change_pmd_r }
/* huge pmd was handled */ - continue; + goto next; } } /* fall through, the trans huge pmd just split */ @@ -196,6 +196,8 @@ static inline unsigned long change_pmd_r this_pages = change_pte_range(vma, pmd, addr, next, newprot, dirty_accountable, prot_numa); pages += this_pages; +next: + cond_resched(); } while (pmd++, addr = next, addr != end);
if (mni_start)
Patches currently in stable-queue which might be from khandual@linux.vnet.ibm.com are
queue-4.14/mm-mprotect-add-a-cond_resched-inside-change_pmd_range.patch