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mm/vmalloc: combine all TLB flush operations of KASAN shadow virtual address into one operation
When compiling kernel source 'make -j $(nproc)' with the up-and-running
KASAN-enabled kernel on a 256-core machine, the following soft lockup is
shown:
watchdog: BUG: soft lockup - CPU#28 stuck for 22s! [kworker/28:1:1760]
CPU: 28 PID: 1760 Comm: kworker/28:1 Kdump: loaded Not tainted 6.10.0-rc5 #95
Workqueue: events drain_vmap_area_work
RIP: 0010:smp_call_function_many_cond+0x1d8/0xbb0
Code: 38 c8 7c 08 84 c9 0f 85 49 08 00 00 8b 45 08 a8 01 74 2e 48 89 f1 49 89 f7 48 c1 e9 03 41 83 e7 07 4c 01 e9 41 83 c7 03 f3 90 <0f> b6 01 41 38 c7 7c 08 84 c0 0f 85 d4 06 00 00 8b 45 08 a8 01 75
RSP: 0018:ffffc9000cb3fb60 EFLAGS: 00000202
RAX: 0000000000000011 RBX: ffff8883bc4469c0 RCX: ffffed10776e9949
RDX: 0000000000000002 RSI: ffff8883bb74ca48 RDI: ffffffff8434dc50
RBP: ffff8883bb74ca40 R08: ffff888103585dc0 R09: ffff8884533a1800
R10: 0000000000000004 R11: ffffffffffffffff R12: ffffed1077888d39
R13: dffffc0000000000 R14: ffffed1077888d38 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff8883bc400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005577b5c8d158 CR3: 0000000004850000 CR4: 0000000000350ef0
Call Trace:
<IRQ>
? watchdog_timer_fn+0x2cd/0x390
? __pfx_watchdog_timer_fn+0x10/0x10
? __hrtimer_run_queues+0x300/0x6d0
? sched_clock_cpu+0x69/0x4e0
? __pfx___hrtimer_run_queues+0x10/0x10
? srso_return_thunk+0x5/0x5f
? ktime_get_update_offsets_now+0x7f/0x2a0
? srso_return_thunk+0x5/0x5f
? srso_return_thunk+0x5/0x5f
? hrtimer_interrupt+0x2ca/0x760
? __sysvec_apic_timer_interrupt+0x8c/0x2b0
? sysvec_apic_timer_interrupt+0x6a/0x90
</IRQ>
<TASK>
? asm_sysvec_apic_timer_interrupt+0x16/0x20
? smp_call_function_many_cond+0x1d8/0xbb0
? __pfx_do_kernel_range_flush+0x10/0x10
on_each_cpu_cond_mask+0x20/0x40
flush_tlb_kernel_range+0x19b/0x250
? srso_return_thunk+0x5/0x5f
? kasan_release_vmalloc+0xa7/0xc0
purge_vmap_node+0x357/0x820
? __pfx_purge_vmap_node+0x10/0x10
__purge_vmap_area_lazy+0x5b8/0xa10
drain_vmap_area_work+0x21/0x30
process_one_work+0x661/0x10b0
worker_thread+0x844/0x10e0
? srso_return_thunk+0x5/0x5f
? __kthread_parkme+0x82/0x140
? __pfx_worker_thread+0x10/0x10
kthread+0x2a5/0x370
? __pfx_kthread+0x10/0x10
ret_from_fork+0x30/0x70
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
Debugging Analysis:
1. The following ftrace log shows that the lockup CPU spends too much
time iterating vmap_nodes and flushing TLB when purging vm_area
structures. (Some info is trimmed).
kworker: funcgraph_entry: | drain_vmap_area_work() {
kworker: funcgraph_entry: | mutex_lock() {
kworker: funcgraph_entry: 1.092 us | __cond_resched();
kworker: funcgraph_exit: 3.306 us | }
... ...
kworker: funcgraph_entry: | flush_tlb_kernel_range() {
... ...
kworker: funcgraph_exit: # 7533.649 us | }
... ...
kworker: funcgraph_entry: 2.344 us | mutex_unlock();
kworker: funcgraph_exit: $ 23871554 us | }
The drain_vmap_area_work() spends over 23 seconds.
There are 2805 flush_tlb_kernel_range() calls in the ftrace log.
* One is called in __purge_vmap_area_lazy().
* Others are called by purge_vmap_node->kasan_release_vmalloc.
purge_vmap_node() iteratively releases kasan vmalloc
allocations and flushes TLB for each vmap_area.
- [Rough calculation] Each flush_tlb_kernel_range() runs
about 7.5ms.
-- 2804 * 7.5ms = 21.03 seconds.
-- That's why a soft lock is triggered.
2. Extending the soft lockup time can work around the issue (For example,
# echo 60 > /proc/sys/kernel/watchdog_thresh). This confirms the
above-mentioned speculation: drain_vmap_area_work() spends too much
time.
If we combine all TLB flush operations of the KASAN shadow virtual
address into one operation in the call path
'purge_vmap_node()->kasan_release_vmalloc()', the running time of
drain_vmap_area_work() can be saved greatly. The idea is from the
flush_tlb_kernel_range() call in __purge_vmap_area_lazy(). And, the
soft lockup won't be triggered.
Here is the test result based on 6.10:
[6.10 wo/ the patch]
1. ftrace latency profiling (record a trace if the latency > 20s).
echo 20000000 > /sys/kernel/debug/tracing/tracing_thresh
echo drain_vmap_area_work > /sys/kernel/debug/tracing/set_graph_function
echo function_graph > /sys/kernel/debug/tracing/current_tracer
echo 1 > /sys/kernel/debug/tracing/tracing_on
2. Run `make -j $(nproc)` to compile the kernel source
3. Once the soft lockup is reproduced, check the ftrace log:
cat /sys/kernel/debug/tracing/trace
# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |
76) $ 50412985 us | } /* __purge_vmap_area_lazy */
76) $ 50412997 us | } /* drain_vmap_area_work */
76) $ 29165911 us | } /* __purge_vmap_area_lazy */
76) $ 29165926 us | } /* drain_vmap_area_work */
91) $ 53629423 us | } /* __purge_vmap_area_lazy */
91) $ 53629434 us | } /* drain_vmap_area_work */
91) $ 28121014 us | } /* __purge_vmap_area_lazy */
91) $ 28121026 us | } /* drain_vmap_area_work */
[6.10 w/ the patch]
1. Repeat step 1-2 in "[6.10 wo/ the patch]"
2. The soft lockup is not triggered and ftrace log is empty.
cat /sys/kernel/debug/tracing/trace
# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |
3. Setting 'tracing_thresh' to 10/5 seconds does not get any ftrace
log.
4. Setting 'tracing_thresh' to 1 second gets ftrace log.
cat /sys/kernel/debug/tracing/trace
# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |
23) $ 1074942 us | } /* __purge_vmap_area_lazy */
23) $ 1074950 us | } /* drain_vmap_area_work */
The worst execution time of drain_vmap_area_work() is about 1 second.
Link: https://lore.kernel.org/lkml/ZqFlawuVnOMY2k3E@pc638.lan/
Link: https://lkml.kernel.org/r/20240726165246.31326-1-ahuang12@lenovo.com
Fixes: 282631cb24 ("mm: vmalloc: remove global purge_vmap_area_root rb-tree")
Signed-off-by: Adrian Huang <ahuang12@lenovo.com>
Co-developed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Tested-by: Jiwei Sun <sunjw10@lenovo.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Adrian Huang
Andrew Morton
parent
15ff4d409e
commit
9e9e085eff
@ -29,6 +29,9 @@ typedef unsigned int __bitwise kasan_vmalloc_flags_t;
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#define KASAN_VMALLOC_VM_ALLOC ((__force kasan_vmalloc_flags_t)0x02u)
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#define KASAN_VMALLOC_PROT_NORMAL ((__force kasan_vmalloc_flags_t)0x04u)
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#define KASAN_VMALLOC_PAGE_RANGE 0x1 /* Apply exsiting page range */
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#define KASAN_VMALLOC_TLB_FLUSH 0x2 /* TLB flush */
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#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
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#include <linux/pgtable.h>
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@ -564,7 +567,8 @@ void kasan_populate_early_vm_area_shadow(void *start, unsigned long size);
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int kasan_populate_vmalloc(unsigned long addr, unsigned long size);
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void kasan_release_vmalloc(unsigned long start, unsigned long end,
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unsigned long free_region_start,
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unsigned long free_region_end);
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unsigned long free_region_end,
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unsigned long flags);
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#else /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
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@ -579,7 +583,8 @@ static inline int kasan_populate_vmalloc(unsigned long start,
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static inline void kasan_release_vmalloc(unsigned long start,
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unsigned long end,
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unsigned long free_region_start,
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unsigned long free_region_end) { }
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unsigned long free_region_end,
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unsigned long flags) { }
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#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
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@ -614,7 +619,8 @@ static inline int kasan_populate_vmalloc(unsigned long start,
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static inline void kasan_release_vmalloc(unsigned long start,
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unsigned long end,
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unsigned long free_region_start,
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unsigned long free_region_end) { }
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unsigned long free_region_end,
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unsigned long flags) { }
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static inline void *kasan_unpoison_vmalloc(const void *start,
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unsigned long size,
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@ -489,7 +489,8 @@ static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
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*/
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void kasan_release_vmalloc(unsigned long start, unsigned long end,
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unsigned long free_region_start,
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unsigned long free_region_end)
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unsigned long free_region_end,
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unsigned long flags)
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{
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void *shadow_start, *shadow_end;
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unsigned long region_start, region_end;
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@ -522,12 +523,17 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
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__memset(shadow_start, KASAN_SHADOW_INIT, shadow_end - shadow_start);
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return;
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}
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apply_to_existing_page_range(&init_mm,
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if (flags & KASAN_VMALLOC_PAGE_RANGE)
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apply_to_existing_page_range(&init_mm,
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(unsigned long)shadow_start,
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size, kasan_depopulate_vmalloc_pte,
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NULL);
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flush_tlb_kernel_range((unsigned long)shadow_start,
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(unsigned long)shadow_end);
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if (flags & KASAN_VMALLOC_TLB_FLUSH)
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flush_tlb_kernel_range((unsigned long)shadow_start,
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(unsigned long)shadow_end);
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}
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}
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34
mm/vmalloc.c
34
mm/vmalloc.c
@ -2182,6 +2182,25 @@ decay_va_pool_node(struct vmap_node *vn, bool full_decay)
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reclaim_list_global(&decay_list);
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}
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static void
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kasan_release_vmalloc_node(struct vmap_node *vn)
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{
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struct vmap_area *va;
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unsigned long start, end;
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start = list_first_entry(&vn->purge_list, struct vmap_area, list)->va_start;
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end = list_last_entry(&vn->purge_list, struct vmap_area, list)->va_end;
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list_for_each_entry(va, &vn->purge_list, list) {
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if (is_vmalloc_or_module_addr((void *) va->va_start))
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kasan_release_vmalloc(va->va_start, va->va_end,
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va->va_start, va->va_end,
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KASAN_VMALLOC_PAGE_RANGE);
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}
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kasan_release_vmalloc(start, end, start, end, KASAN_VMALLOC_TLB_FLUSH);
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}
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static void purge_vmap_node(struct work_struct *work)
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{
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struct vmap_node *vn = container_of(work,
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@ -2190,20 +2209,17 @@ static void purge_vmap_node(struct work_struct *work)
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struct vmap_area *va, *n_va;
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LIST_HEAD(local_list);
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if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
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kasan_release_vmalloc_node(vn);
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vn->nr_purged = 0;
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list_for_each_entry_safe(va, n_va, &vn->purge_list, list) {
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unsigned long nr = va_size(va) >> PAGE_SHIFT;
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unsigned long orig_start = va->va_start;
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unsigned long orig_end = va->va_end;
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unsigned int vn_id = decode_vn_id(va->flags);
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list_del_init(&va->list);
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if (is_vmalloc_or_module_addr((void *)orig_start))
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kasan_release_vmalloc(orig_start, orig_end,
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va->va_start, va->va_end);
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nr_purged_pages += nr;
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vn->nr_purged++;
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@ -4784,7 +4800,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
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&free_vmap_area_list);
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if (va)
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kasan_release_vmalloc(orig_start, orig_end,
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va->va_start, va->va_end);
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va->va_start, va->va_end,
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KASAN_VMALLOC_PAGE_RANGE | KASAN_VMALLOC_TLB_FLUSH);
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vas[area] = NULL;
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}
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@ -4834,7 +4851,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
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&free_vmap_area_list);
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if (va)
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kasan_release_vmalloc(orig_start, orig_end,
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va->va_start, va->va_end);
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va->va_start, va->va_end,
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KASAN_VMALLOC_PAGE_RANGE | KASAN_VMALLOC_TLB_FLUSH);
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vas[area] = NULL;
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kfree(vms[area]);
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}
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