From 795e7efec6ea7e9d597c3fced9f5307fae467cb0 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 19 Dec 2024 16:08:54 -0800 Subject: srcu: Make SRCU readers use ->srcu_ctrs for counter selection This commit causes SRCU readers to use ->srcu_ctrs for counter selection instead of ->srcu_idx. This takes another step towards array-indexing-free SRCU readers. [ paulmck: Apply kernel test robot feedback. ] Co-developed-by: Z qiang Signed-off-by: Z qiang Signed-off-by: Paul E. McKenney Tested-by: kernel test robot Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: Signed-off-by: Boqun Feng --- include/linux/srcutree.h | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index c794d599db5c..1b01ced61a45 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -101,6 +101,7 @@ struct srcu_usage { */ struct srcu_struct { unsigned int srcu_idx; /* Current rdr array element. */ + struct srcu_ctr __percpu *srcu_ctrp; struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ struct lockdep_map dep_map; struct srcu_usage *srcu_sup; /* Update-side data. */ @@ -167,6 +168,7 @@ struct srcu_struct { #define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name) \ { \ .sda = &pcpu_name, \ + .srcu_ctrp = &pcpu_name.srcu_ctrs[0], \ __SRCU_STRUCT_INIT_COMMON(name, usage_name) \ } @@ -222,13 +224,12 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); */ static inline int __srcu_read_lock_lite(struct srcu_struct *ssp) { - int idx; + struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp); RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite()."); - idx = READ_ONCE(ssp->srcu_idx) & 0x1; - this_cpu_inc(ssp->sda->srcu_ctrs[idx].srcu_locks.counter); /* Y */ + this_cpu_inc(scp->srcu_locks.counter); /* Y */ barrier(); /* Avoid leaking the critical section. */ - return idx; + return scp - &ssp->sda->srcu_ctrs[0]; } /* -- cgit v1.2.3