On Thu, Sep 17, 2020 at 1:58 PM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > > On Wed, Sep 16, 2020 at 02:37:30PM -0700, Paul E. McKenney wrote: > > So here are a few questions that I would ask: > > Oh, and this one: > > 0. Did someone call srcu_read_lock() before init_srcu_struct() > had been called on this srcu_struct structure? > > Thanx, Paul > > > 1. Did the init_srcu_struct() for this srcu_struct report an error? > > (Though with current mainline, that memory-allocation failure > > would more likely have page-faulted in init_srcu_struct().) > > > > 2. Has the srcu_struct in question already been passed to > > cleanup_srcu_struct()? > > > > 3. Has the value of %fs been clobbered? Though that seems > > unlikely given that it also happens on aarch64. Plus, the > > smoking gun seems to me to be the zero value of %eax. > > > > 4. If the above three questions fail to provide enlightenment, > > I suggest recording the ->sda value and adding debug checks > > to anything that can unmap memory... And recording the value > > of ->sda somewhere to check to see if it is being changed (it > > should remain constant from init_srcu_struct()'s return through > > the corresponding call to cleanup_srcu_struct()). > > > > Please let me know how it goes! Thanks for the tips Paul. I've copied your suggestions into the bug report with additional suggestions for the reporters to collect more info, particularly in the arm64 case. I will update this thread once we've resolved the report. -- Thanks, ~Nick Desaulniers
