From 9407f5c3ec10c155aae61fc4496a7c17a96907b4 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 11 Nov 2024 16:28:51 -0800 Subject: srcu: Unconditionally record srcu_read_lock_lite() in ->srcu_reader_flavor Currently, srcu_read_lock_lite() uses the SRCU_READ_FLAVOR_LITE bit in ->srcu_reader_flavor to communicate to the grace-period processing in srcu_readers_active_idx_check() that the smp_mb() must be replaced by a synchronize_rcu(). Unfortunately, ->srcu_reader_flavor is not updated unless the kernel is built with CONFIG_PROVE_RCU=y. Therefore in all kernels built with CONFIG_PROVE_RCU=n, srcu_readers_active_idx_check() incorrectly uses smp_mb() instead of synchronize_rcu() for srcu_struct structures whose readers use srcu_read_lock_lite(). This commit therefore causes Tree SRCU srcu_read_lock_lite() to unconditionally update ->srcu_reader_flavor so that srcu_readers_active_idx_check() can make the correct choice. Reported-by: Neeraj Upadhyay Closes: https://lore.kernel.org/all/d07e8f4a-d5ff-4c8e-8e61-50db285c57e9@amd.com/ Fixes: c0f08d6b5a61 ("srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite()") Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Reviewed-by: Neeraj Upadhyay Signed-off-by: Frederic Weisbecker --- include/linux/srcutiny.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/srcutiny.h') diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 4d96bbdb45f0..1321da803274 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -81,6 +81,9 @@ static inline void srcu_barrier(struct srcu_struct *ssp) synchronize_srcu(ssp); } +#define srcu_check_read_flavor(ssp, read_flavor) do { } while (0) +#define srcu_check_read_flavor_lite(ssp) do { } while (0) + /* Defined here to avoid size increase for non-torture kernels. */ static inline void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf) -- cgit v1.2.3