Commit 1607e88b authored by Junxian Huang's avatar Junxian Huang
Browse files

RDMA/hns: Fix soft lockup during bt pages loop 

maillist inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBV0G0
CVE: NA

Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/commit/?h=wip/leon-for-rc&id=25655580136de59ec89f09089dd28008ea440fc9



----------------------------------------------------------------------

Driver runs a for-loop when allocating bt pages and mapping them with
buffer pages. When a large buffer (e.g. MR over 100GB) is being allocated,
it may require a considerable loop count. This will lead to soft lockup:

        watchdog: BUG: soft lockup - CPU#27 stuck for 22s!
        ...
        Call trace:
         hem_list_alloc_mid_bt+0x124/0x394 [hns_roce_hw_v2]
         hns_roce_hem_list_request+0xf8/0x160 [hns_roce_hw_v2]
         hns_roce_mtr_create+0x2e4/0x360 [hns_roce_hw_v2]
         alloc_mr_pbl+0xd4/0x17c [hns_roce_hw_v2]
         hns_roce_reg_user_mr+0xf8/0x190 [hns_roce_hw_v2]
         ib_uverbs_reg_mr+0x118/0x290

        watchdog: BUG: soft lockup - CPU#35 stuck for 23s!
        ...
        Call trace:
         hns_roce_hem_list_find_mtt+0x7c/0xb0 [hns_roce_hw_v2]
         mtr_map_bufs+0xc4/0x204 [hns_roce_hw_v2]
         hns_roce_mtr_create+0x31c/0x3c4 [hns_roce_hw_v2]
         alloc_mr_pbl+0xb0/0x160 [hns_roce_hw_v2]
         hns_roce_reg_user_mr+0x108/0x1c0 [hns_roce_hw_v2]
         ib_uverbs_reg_mr+0x120/0x2bc

Add a cond_resched() to fix soft lockup during these loops. In order not
to affect the allocation performance of normal-size buffer, set the loop
count of a 100GB MR as the threshold to call cond_resched().

Fixes: 38389eaa ("RDMA/hns: Add mtr support for mixed multihop addressing")
Signed-off-by: default avatarJunxian Huang <huangjunxian6@hisilicon.com>
Link: https://patch.msgid.link/20250311084857.3803665-3-huangjunxian6@hisilicon.com


Signed-off-by: default avatarLeon Romanovsky <leon@kernel.org>
Signed-off-by: default avatarXinghai Cen <cenxinghai@h-partners.com>
parent 1579902a

drivers/infiniband/hw/hns/hns_roce_hem.c

+15 −1
Original line number Diff line number Diff line
@@ -1362,6 +1362,11 @@ static int hem_list_alloc_root_bt(struct hns_roce_dev *hr_dev, 
	return ret;

}



/* This is the bottom bt pages number of a 100G MR on 4K OS, assuming

 * the bt page size is not expanded by cal_best_bt_pg_sz()

 */

#define RESCHED_LOOP_CNT_THRESHOLD_ON_4K 12800



/* construct the base address table and link them by address hop config */

int hns_roce_hem_list_request(struct hns_roce_dev *hr_dev,

			      struct hns_roce_hem_list *hem_list,
@@ -1370,6 +1375,7 @@ int hns_roce_hem_list_request(struct hns_roce_dev *hr_dev, 
{

	const struct hns_roce_buf_region *r;

	int ofs, end;

	int loop;

	int unit;

	int ret;

	int i;
@@ -1387,7 +1393,10 @@ int hns_roce_hem_list_request(struct hns_roce_dev *hr_dev, 
			continue;



		end = r->offset + r->count;

		for (ofs = r->offset; ofs < end; ofs += unit) {

		for (ofs = r->offset, loop = 1; ofs < end; ofs += unit, loop++) {

			if (!(loop % RESCHED_LOOP_CNT_THRESHOLD_ON_4K))

				cond_resched();



			ret = hem_list_alloc_mid_bt(hr_dev, r, unit, ofs,

						    hem_list->mid_bt[i],

						    &hem_list->btm_bt);
@@ -1444,9 +1453,14 @@ void *hns_roce_hem_list_find_mtt(struct hns_roce_dev *hr_dev, 
	struct list_head *head = &hem_list->btm_bt;

	struct hns_roce_hem_item *hem, *temp_hem;

	void *cpu_base = NULL;

	int loop = 1;

	int nr = 0;



	list_for_each_entry_safe(hem, temp_hem, head, sibling) {

		if (!(loop % RESCHED_LOOP_CNT_THRESHOLD_ON_4K))

			cond_resched();

		loop++;



		if (hem_list_page_is_in_range(hem, offset)) {

			nr = offset - hem->start;

			cpu_base = hem->addr + nr * BA_BYTE_LEN;