On Sun, Jan 04, 2026 at 04:10:27PM +0800, Donglin Peng wrote: > From: Donglin Peng <[email protected]> > > The RCU stall warning message includes an "idle=" field to indicate > the dyntick-idle state of a CPU. According to Documentation/RCU/stallwarn.rst, > the hexadecimal number before the first '/' represents the low-order 16 > bits of the dynticks counter. An even value denotes that the CPU is in > dyntick-idle mode, while an odd value indicates otherwise. > > This was accurate until commit 171476775d32 ("context_tracking: Convert state > to atomic_t"), > which merged the context tracking state and the dynticks counter into a > single atomic value. Consequently, the value printed in the stall warning > no longer directly corresponds to the documented dynticks counter bits. > > To restore consistency between the code's output and the documentation, > right-shift the merged atomic state value to extract and display the > correct low-order bits of the dynticks counter. > > Fixes: 171476775d32 ("context_tracking: Convert state to atomic_t") > Signed-off-by: Donglin Peng <[email protected]>
Looks good to me! Also nice use of ilog2() which resolves to a single shift right instruction per my testing (shift right of 2). Reviewed-by: Joel Fernandes <[email protected]> thanks, - Joel > --- > kernel/rcu/tree_stall.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h > index b67532cb8770..d25cc826d77a 100644 > --- a/kernel/rcu/tree_stall.h > +++ b/kernel/rcu/tree_stall.h > @@ -555,7 +555,7 @@ static void print_cpu_stall_info(int cpu) > rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' : > "!."[!delta], > ticks_value, ticks_title, > - ct_rcu_watching_cpu(cpu) & 0xffff, > + (ct_rcu_watching_cpu(cpu) >> ilog2(CT_RCU_WATCHING)) & 0xffff, > ct_nesting_cpu(cpu), ct_nmi_nesting_cpu(cpu), > rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), > data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart, > -- > 2.34.1 >
