Messages in this thread | | | Date | Thu, 16 Mar 2023 10:01:58 +0800 | Subject | Re: [PATCH v2] swiotlb: fix the deadlock in swiotlb_do_find_slots | From | Guorui Yu <> |
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Hi Christoph,
Thanks for your reply, and this new version looks go to me.
Yours sincerely, Guorui
在 2023/3/15 22:47, Christoph Hellwig 写道: > I think this looks generall fine, but the index_nowrap variable > name seems very confusing. What about this slighlt adjusted > version? > > --- > From 11559745f0920b53ba5f8b2fc6241891e1dfcf4b Mon Sep 17 00:00:00 2001 > From: "GuoRui.Yu" <GuoRui.Yu@linux.alibaba.com> > Subject: swiotlb: fix the deadlock in swiotlb_do_find_slots > > In general, if swiotlb is sufficient, the logic of index = > wrap_area_index(mem, index + 1) is fine, it will quickly take a slot and > release the area->lock; But if swiotlb is insufficient and the device > has min_align_mask requirements, such as NVME, we may not be able to > satisfy index == wrap and exit the loop properly. In this case, other > kernel threads will not be able to acquire the area->lock and release > the slot, resulting in a deadlock. > > The current implementation of wrap_area_index does not involve a modulo > operation, so adjusting the wrap to ensure the loop ends is not trivial. > Introduce a new variable to record the number of loops and exit the loop > after completing the traversal. > > Backtraces: > Other CPUs are waiting this core to exit the swiotlb_do_find_slots > loop. > [10199.924391] RIP: 0010:swiotlb_do_find_slots+0x1fe/0x3e0 > [10199.924403] Call Trace: > [10199.924404] <TASK> > [10199.924405] swiotlb_tbl_map_single+0xec/0x1f0 > [10199.924407] swiotlb_map+0x5c/0x260 > [10199.924409] ? nvme_pci_setup_prps+0x1ed/0x340 > [10199.924411] dma_direct_map_page+0x12e/0x1c0 > [10199.924413] nvme_map_data+0x304/0x370 > [10199.924415] nvme_prep_rq.part.0+0x31/0x120 > [10199.924417] nvme_queue_rq+0x77/0x1f0 > > ... > [ 9639.596311] NMI backtrace for cpu 48 > [ 9639.596336] Call Trace: > [ 9639.596337] > [ 9639.596338] _raw_spin_lock_irqsave+0x37/0x40 > [ 9639.596341] swiotlb_do_find_slots+0xef/0x3e0 > [ 9639.596344] swiotlb_tbl_map_single+0xec/0x1f0 > [ 9639.596347] swiotlb_map+0x5c/0x260 > [ 9639.596349] dma_direct_map_sg+0x7a/0x280 > [ 9639.596352] __dma_map_sg_attrs+0x30/0x70 > [ 9639.596355] dma_map_sgtable+0x1d/0x30 > [ 9639.596356] nvme_map_data+0xce/0x370 > > ... > [ 9639.595665] NMI backtrace for cpu 50 > [ 9639.595682] Call Trace: > [ 9639.595682] > [ 9639.595683] _raw_spin_lock_irqsave+0x37/0x40 > [ 9639.595686] swiotlb_release_slots.isra.0+0x86/0x180 > [ 9639.595688] dma_direct_unmap_sg+0xcf/0x1a0 > [ 9639.595690] nvme_unmap_data.part.0+0x43/0xc0 > > Fixes: 1f221a0d0dbf ("swiotlb: respect min_align_mask") > Signed-off-by: GuoRui.Yu <GuoRui.Yu@linux.alibaba.com> > Signed-off-by: Xiaokang Hu <xiaokang.hxk@alibaba-inc.com> > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > kernel/dma/swiotlb.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 03e3251cd9d2b6..91454b513db069 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -625,8 +625,8 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index, > unsigned int iotlb_align_mask = > dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1); > unsigned int nslots = nr_slots(alloc_size), stride; > - unsigned int index, wrap, count = 0, i; > unsigned int offset = swiotlb_align_offset(dev, orig_addr); > + unsigned int index, slots_checked, count = 0, i; > unsigned long flags; > unsigned int slot_base; > unsigned int slot_index; > @@ -649,15 +649,16 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index, > goto not_found; > > slot_base = area_index * mem->area_nslabs; > - index = wrap = wrap_area_index(mem, ALIGN(area->index, stride)); > + index = wrap_area_index(mem, ALIGN(area->index, stride)); > > - do { > + for (slots_checked = 0; slots_checked < mem->area_nslabs; ) { > slot_index = slot_base + index; > > if (orig_addr && > (slot_addr(tbl_dma_addr, slot_index) & > iotlb_align_mask) != (orig_addr & iotlb_align_mask)) { > index = wrap_area_index(mem, index + 1); > + slots_checked++; > continue; > } > > @@ -673,7 +674,8 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index, > goto found; > } > index = wrap_area_index(mem, index + stride); > - } while (index != wrap); > + slots_checked += stride; > + } > > not_found: > spin_unlock_irqrestore(&area->lock, flags);
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