bpf stackmap with build-id lookup (BPF_F_STACK_BUILD_ID) can trigger A-A deadlock on rq_lock(): rcu: INFO: rcu_sched detected stalls on CPUs/tasks: [...] Call Trace: try_to_wake_up+0x1ad/0x590 wake_up_q+0x54/0x80 rwsem_wake+0x8a/0xb0 bpf_get_stack+0x13c/0x150 bpf_prog_fbdaf42eded9fe46_on_event+0x5e3/0x1000 bpf_overflow_handler+0x60/0x100 __perf_event_overflow+0x4f/0xf0 perf_swevent_overflow+0x99/0xc0 ___perf_sw_event+0xe7/0x120 __schedule+0x47d/0x620 schedule+0x29/0x90 futex_wait_queue_me+0xb9/0x110 futex_wait+0x139/0x230 do_futex+0x2ac/0xa50 __x64_sys_futex+0x13c/0x180 do_syscall_64+0x42/0x100 entry_SYSCALL_64_after_hwframe+0x44/0xa9 For more details on how to reproduce this is error, please refer to 2/2. Fix this issue by checking a new helper this_rq_is_locked(). If the rq_lock is already locked, postpone up_read() in irq_work, just like the in_nmi() case. Song Liu (2): sched: introduce this_rq_is_locked() bpf/stackmap: fix A-A deadlock in bpf_get_stack() include/linux/sched.h | 1 + kernel/bpf/stackmap.c | 2 +- kernel/sched/core.c | 8 ++++++++ 3 files changed, 10 insertions(+), 1 deletion(-) -- 2.17.1
