mm/vunmap: Add cond_resched() in vunmap_pmd_range
Subsystems (2)
PATCH 1/1 mm/vunmap: Add cond_resched() in vunmap_pmd_range
Like zap_pte_range add cond_resched so that we can avoid softlockups as reported below. On non-preemptible kernel with large I/O map region (like the one we get when using persistent memory with sector mode), an unmap of the namespace can report below softlockups.
22724.027334] watchdog: BUG: soft lockup - CPU#49 stuck for 23s! [ndctl:50777]
NIP [c0000000000dc224] plpar_hcall+0x38/0x58
LR [c0000000000d8898] pSeries_lpar_hpte_invalidate+0x68/0xb0
Call Trace: [c0000004e87a7780] [c0000004fb197c00] 0xc0000004fb197c00 (unreliable) [c0000004e87a7810] [c00000000007f4e4] flush_hash_page+0x114/0x200 [c0000004e87a7890] [c0000000000833cc] hpte_need_flush+0x2dc/0x540 [c0000004e87a7950] [c0000000003f5798] vunmap_page_range+0x538/0x6f0 [c0000004e87a7a70] [c0000000003f76d0] free_unmap_vmap_area+0x30/0x70 [c0000004e87a7aa0] [c0000000003f7a6c] remove_vm_area+0xfc/0x140 [c0000004e87a7ad0] [c0000000003f7dd8] __vunmap+0x68/0x270 [c0000004e87a7b50] [c000000000079de4] __iounmap.part.0+0x34/0x60 [c0000004e87a7bb0] [c000000000376394] memunmap+0x54/0x70 [c0000004e87a7bd0] [c000000000881d7c] release_nodes+0x28c/0x300 [c0000004e87a7c40] [c00000000087a65c] device_release_driver_internal+0x16c/0x280 [c0000004e87a7c80] [c000000000876fc4] unbind_store+0x124/0x170 [c0000004e87a7cd0] [c000000000875be4] drv_attr_store+0x44/0x60 [c0000004e87a7cf0] [c00000000057c734] sysfs_kf_write+0x64/0x90 [c0000004e87a7d10] [c00000000057bc10] kernfs_fop_write+0x1b0/0x290 [c0000004e87a7d60] [c000000000488e6c] __vfs_write+0x3c/0x70 [c0000004e87a7d80] [c00000000048c868] vfs_write+0xd8/0x260 [c0000004e87a7dd0] [c00000000048ccac] ksys_write+0xdc/0x130 [c0000004e87a7e20] [c00000000000b588] system_call+0x5c/0x70
--- mm/vmalloc.c | 2 ++ 1 file changed, 2 insertions(+)
mm/vmalloc.c +2 -0
@@ -102,6 +102,8 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,if (pmd_none_or_clear_bad (pmd))continue ;vunmap_pte_range (pmd, addr, next, mask); + +cond_resched (); }while (pmd++, addr = next, addr != end); }
Signature · 1 line
2.26.2
Andrew Morton
maintainerQuoted 10 lines · On Fri, 7 Aug 2020 13:29:33 +0530 "Aneesh Kumar K.V"…
Like
zap_pte_rangeaddcond_reschedso that we can avoid softlockups as reported below. On non-preemptible kernel with large I/O map region (like the one we get when using persistent memory with sector mode), an unmap of the namespace can report below softlockups....
mm/vmalloc.c static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, · line 108
Quoted 7 lines
mm/vmalloc.c +2
-0@@ -102,6 +102,8 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,if (pmd_none_or_clear_bad (pmd))continue ;vunmap_pte_range (pmd, addr, next, mask); + +cond_resched (); }while (pmd++, addr = next, addr != end); }
That looks sane. I'll aim for merging it in 5.9-rc2ish, with a cc:stable, OK?
Quoted 9 lines · Andrew Morton
Quoted 7 lines · On Fri, 7 Aug 2020 13:29:33 +0530 "Aneesh Kumar K.V"…
Like
zap_pte_rangeaddcond_reschedso that we can avoid softlockups as reported below. On non-preemptible kernel with large I/O map region (like the one we get when using persistent memory with sector mode), an unmap of the namespace can report below softlockups....
Quoted 14 lines
mm/vmalloc.c static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, · line 108
Quoted 10 lines
mm/vmalloc.c +2
-0@@ -102,6 +102,8 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,if (pmd_none_or_clear_bad (pmd))continue ;vunmap_pte_range (pmd, addr, next, mask); + +cond_resched (); }while (pmd++, addr = next, addr != end); }That looks sane. I'll aim for merging it in 5.9-rc2ish, with a cc:stable, OK?
Sure. I was not so particular about stable because it was only a softlockup warning.
-aneesh