Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> writes: > On Wed, Apr 14, 2021 at 10:52 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: >> >> > > > > if (num_online_cpus() > 1) >> > > > > synchronize_rcu(); >> >> In CONFIG_PREEMPT_NONE=y and CONFIG_PREEMPT_VOLUNTARY=y kernels, this >> synchronize_rcu() will be a no-op anyway due to there only being the >> one CPU. Or are these failures all happening in CONFIG_PREEMPT=y kernels, >> and in tests where preemption could result in the observed failures? >> >> Could you please send your .config file, or at least the relevant portions >> of it? > > That's my understanding as well. I assumed Toke has preempt=y. > Otherwise the whole thing needs to be root caused properly. Running with a single CPU fails, with multiple CPUs succeeds. Happens without PREEMPT as well: $ egrep 'HZ|PREEMPT|RCU' .config CONFIG_NO_HZ_COMMON=y # CONFIG_HZ_PERIODIC is not set CONFIG_NO_HZ_IDLE=y # CONFIG_NO_HZ_FULL is not set CONFIG_NO_HZ=y # CONFIG_PREEMPT_NONE is not set CONFIG_PREEMPT_VOLUNTARY=y # CONFIG_PREEMPT is not set # RCU Subsystem CONFIG_TREE_RCU=y CONFIG_RCU_EXPERT=y CONFIG_SRCU=y CONFIG_TREE_SRCU=y CONFIG_TASKS_RCU_GENERIC=y CONFIG_TASKS_RUDE_RCU=y CONFIG_TASKS_TRACE_RCU=y CONFIG_RCU_STALL_COMMON=y CONFIG_RCU_NEED_SEGCBLIST=y CONFIG_RCU_FANOUT=64 CONFIG_RCU_FANOUT_LEAF=16 # CONFIG_RCU_FAST_NO_HZ is not set # CONFIG_RCU_NOCB_CPU is not set # CONFIG_TASKS_TRACE_RCU_READ_MB is not set # end of RCU Subsystem # CONFIG_HZ_100 is not set CONFIG_HZ_250=y # CONFIG_HZ_300 is not set # CONFIG_HZ_1000 is not set CONFIG_HZ=250 CONFIG_MMU_GATHER_RCU_TABLE_FREE=y CONFIG_HAVE_PREEMPT_DYNAMIC=y CONFIG_PREEMPT_NOTIFIERS=y # CONFIG_MACHZ_WDT is not set # RCU Debugging # CONFIG_RCU_SCALE_TEST is not set # CONFIG_RCU_TORTURE_TEST is not set # CONFIG_RCU_REF_SCALE_TEST is not set CONFIG_RCU_CPU_STALL_TIMEOUT=60 # CONFIG_RCU_TRACE is not set # CONFIG_RCU_EQS_DEBUG is not set # CONFIG_RCU_STRICT_GRACE_PERIOD is not set # end of RCU Debugging # CONFIG_PREEMPTIRQ_DELAY_TEST is not set Anything else you need from .config? -Toke
