From: Guo Xuenan guoxuenan@huawei.com

hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5930C

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when set up sq ring size with IORING_MAX_ENTRIES, io_submit_sqes may looping ~32768 times which may trigger soft lockups. add cond_resched condition to avoid this bad situation.

set sq ring size 32768 to perform stress test as follows:

watchdog: BUG: soft lockup - CPU#3 stuck for 26s! [poc:691] Modules linked in: CPU: 3 PID: 691 Comm: poc Not tainted 5.18.0+ #9 Hardware name: linux,dummy-virt (DT) pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : arch_local_irq_enable+0xc/0x28 lr : io_issue_sqe+0x870/0x28e8 sp : ffff80000e0f7800 x29: ffff80000e0f7800 x28: ffff0000cf850dd0 x27: ffff0000cf2c2000 x26: ffff8000096f4b20 x25: ffff0000cd769c00 x24: ffff0000c12b6650 x23: ffff800009dad958 x22: 00000006fc23ac00 x21: ffff0000cd769c08 x20: 1ffff00001c1ef1a x19: ffff0000cd767e00 x18: 0000000000000000 x17: ffff800008032b74 x16: ffff800008636448 x15: 0000fffff7166568 x14: ffff80000861edf0 x13: ffff600019e58449 x12: 1fffe00019e58448 x11: 1fffe00019e58448 x10: ffff600019e58448 x9 : dfff800000000000 x8 : ffff0000cf2c2244 x7 : 0000000000000001 x6 : ffff600019e58449 x5 : ffff600019e58449 x4 : ffff600019e58449 x3 : ffff8000086306c0 x2 : 0000000000000001 x1 : ffff0000cf2c2244 x0 : 00000000000000e0 Call trace: arch_local_irq_enable+0xc/0x28 io_submit_sqes+0x530/0x29d8 __arm64_sys_io_uring_enter+0x380/0xd18 invoke_syscall+0x64/0x180 el0_svc_common.constprop.2+0x178/0x208 do_el0_svc+0x84/0xa0 el0_svc+0x48/0x1a0 el0t_64_sync_handler+0x90/0xb8 el0t_64_sync+0x180/0x184 Kernel panic - not syncing: softlockup: hung tasks CPU: 3 PID: 691 Comm: poc Tainted: G L 5.18.0+ #9 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x218/0x228 show_stack+0x20/0x68 dump_stack_lvl+0x68/0x84 dump_stack+0x1c/0x38 panic+0x1ec/0x3ec watchdog_timer_fn+0x28c/0x300 __hrtimer_run_queues+0x1d8/0x498 hrtimer_interrupt+0x238/0x558 arch_timer_handler_virt+0x48/0x60 handle_percpu_devid_irq+0xdc/0x270 generic_handle_domain_irq+0x50/0x70 gic_handle_irq+0x8c/0x4bc call_on_irq_stack+0x2c/0x38 do_interrupt_handler+0xc4/0xc8 el1_interrupt+0x48/0xb0 el1h_64_irq_handler+0x18/0x28 el1h_64_irq+0x74/0x78 arch_local_irq_enable+0xc/0x28 io_submit_sqes+0x530/0x29d8 __arm64_sys_io_uring_enter+0x380/0xd18 invoke_syscall+0x64/0x180 el0_svc_common.constprop.2+0x178/0x208 do_el0_svc+0x84/0xa0 el0_svc+0x48/0x1a0 el0t_64_sync_handler+0x90/0xb8 el0t_64_sync+0x180/0x184 SMP: stopping secondary CPUs Kernel Offset: disabled CPU features: 0x110,00008f09,00001006 Memory Limit: none ---[ end Kernel panic - not syncing: softlockup: hung tasks ]---

Link: https://lore.kernel.org/all/d4bc3afb-02d5-1793-cffa-e15b2bdb0028@huawei.com/ Signed-off-by: Guo Xuenan guoxuenan@huawei.com

Conflict: io_uring/io_uring.c

Signed-off-by: Li Lingfeng lilingfeng3@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Reviewed-by: Wang Weiyang wangweiyang2@huawei.com Signed-off-by: Jialin Zhang zhangjialin11@huawei.com Signed-off-by: Zizhi Wo wozizhi@huawei.com --- io_uring/io_uring.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 8d1bc6cdfe71..d79e78971ec5 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2440,6 +2440,9 @@ int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr) left--; break; } + /* to avoid doing too much in one submit round */ + if (left > IORING_MAX_ENTRIES / 2) + cond_resched(); } while (--left);

if (unlikely(left)) {