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McKenney wrote: > On Tue, Nov 10, 2026 at 02:28:43PM -0500, Mathieu Desnoyers wrote: [...] > A good addition! Vanilla RCU could benefit from this as well, but that > can be done later. Thanks! [...] >> + if (READ_ONCE(p->rtort_pipe_count) > 1) >> + atomic_inc(&n_rcu_torture_error); > > Doesn't this miss doing a splat on RCU too-short grace period? [...] > Maybe a separate global array for NMIs, parallel to the "Reader Pipe:" > and "Reader Batch:" arrays, that is atomically updated and printed > separately, maybe "NMI Reader Pipe:" or similar? > > Or is there a better way? It does miss it. The test still ends in FAILURE. But there is no "!!!", no warning, and nothing in "Reader Pipe:". v2 takes your approach. The NMI reader counts its pipe and batch values in two arrays of atomic_long_t. rcu_torture_stats_print() prints them as "NMI Reader Pipe:" and "NMI Reader Batch:", only when readers ran in NMI. A too-short grace period in NMI joins the "!!!" condition, with its own WARN_ON_ONCE(). So the other readers keep their this_cpu_inc(). The NMI reader skips the trace event and rcu_ftrace_dump() of the other readers. The "!!!" and the warning then come from the statistics kthread. I checked it with a mutation that makes every NMI reader see a pipe count of 2: the run splats as expected. [...] >> cur_ops->call(&rtncp->rh, rcu_torture_nmi_invoked); > > OK, the invocation of ->call() without testing ->call() is OK because > rcu_torture_nmi_do_calls never gets set if ->call() is NULL. Yes. Thanks! Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com