| From 6639494327ff7400b1d3a0a24400a281c6d80bf8 Mon Sep 17 00:00:00 2001 |
| From: Adrian Huang <ahuang12@lenovo.com> |
| Date: Mon, 13 Jan 2020 16:29:32 -0800 |
| Subject: [PATCH] mm: memcg/slab: call flush_memcg_workqueue() only if memcg |
| workqueue is valid |
| |
| commit 2fe20210fc5f5e62644678b8f927c49f2c6f42a7 upstream. |
| |
| When booting with amd_iommu=off, the following WARNING message |
| appears: |
| |
| AMD-Vi: AMD IOMMU disabled on kernel command-line |
| ------------[ cut here ]------------ |
| WARNING: CPU: 0 PID: 0 at kernel/workqueue.c:2772 flush_workqueue+0x42e/0x450 |
| Modules linked in: |
| CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.5.0-rc3-amd-iommu #6 |
| Hardware name: Lenovo ThinkSystem SR655-2S/7D2WRCZ000, BIOS D8E101L-1.00 12/05/2019 |
| RIP: 0010:flush_workqueue+0x42e/0x450 |
| Code: ff 0f 0b e9 7a fd ff ff 4d 89 ef e9 33 fe ff ff 0f 0b e9 7f fd ff ff 0f 0b e9 bc fd ff ff 0f 0b e9 a8 fd ff ff e8 52 2c fe ff <0f> 0b 31 d2 48 c7 c6 e0 88 c5 95 48 c7 c7 d8 ad f0 95 e8 19 f5 04 |
| Call Trace: |
| kmem_cache_destroy+0x69/0x260 |
| iommu_go_to_state+0x40c/0x5ab |
| amd_iommu_prepare+0x16/0x2a |
| irq_remapping_prepare+0x36/0x5f |
| enable_IR_x2apic+0x21/0x172 |
| default_setup_apic_routing+0x12/0x6f |
| apic_intr_mode_init+0x1a1/0x1f1 |
| x86_late_time_init+0x17/0x1c |
| start_kernel+0x480/0x53f |
| secondary_startup_64+0xb6/0xc0 |
| ---[ end trace 30894107c3749449 ]--- |
| x2apic: IRQ remapping doesn't support X2APIC mode |
| x2apic disabled |
| |
| The warning is caused by the calling of 'kmem_cache_destroy()' |
| in free_iommu_resources(). Here is the call path: |
| |
| free_iommu_resources |
| kmem_cache_destroy |
| flush_memcg_workqueue |
| flush_workqueue |
| |
| The root cause is that the IOMMU subsystem runs before the workqueue |
| subsystem, which the variable 'wq_online' is still 'false'. This leads |
| to the statement 'if (WARN_ON(!wq_online))' in flush_workqueue() is |
| 'true'. |
| |
| Since the variable 'memcg_kmem_cache_wq' is not allocated during the |
| time, it is unnecessary to call flush_memcg_workqueue(). This prevents |
| the WARNING message triggered by flush_workqueue(). |
| |
| Link: http://lkml.kernel.org/r/20200103085503.1665-1-ahuang12@lenovo.com |
| Fixes: 92ee383f6daab ("mm: fix race between kmem_cache destroy, create and deactivate") |
| Signed-off-by: Adrian Huang <ahuang12@lenovo.com> |
| Reported-by: Xiaochun Lee <lixc17@lenovo.com> |
| Reviewed-by: Shakeel Butt <shakeelb@google.com> |
| Cc: Joerg Roedel <jroedel@suse.de> |
| Cc: Christoph Lameter <cl@linux.com> |
| Cc: Pekka Enberg <penberg@kernel.org> |
| Cc: David Rientjes <rientjes@google.com> |
| Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> |
| Cc: Michal Hocko <mhocko@kernel.org> |
| Cc: Johannes Weiner <hannes@cmpxchg.org> |
| Cc: <stable@vger.kernel.org> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/mm/slab_common.c b/mm/slab_common.c |
| index 45f86ddc2637..6806442b77bb 100644 |
| --- a/mm/slab_common.c |
| +++ b/mm/slab_common.c |
| @@ -877,7 +877,8 @@ static void flush_memcg_workqueue(struct kmem_cache *s) |
| * deactivates the memcg kmem_caches through workqueue. Make sure all |
| * previous workitems on workqueue are processed. |
| */ |
| - flush_workqueue(memcg_kmem_cache_wq); |
| + if (likely(memcg_kmem_cache_wq)) |
| + flush_workqueue(memcg_kmem_cache_wq); |
| |
| /* |
| * If we're racing with children kmem_cache deactivation, it might |
| -- |
| 2.7.4 |
| |
