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| author | Paul E. McKenney <paulmck@kernel.org> | 2024-11-11 16:28:51 -0800 |
|---|---|---|
| committer | Frederic Weisbecker <frederic@kernel.org> | 2024-11-15 22:13:37 +0100 |
| commit | 9407f5c3ec10c155aae61fc4496a7c17a96907b4 (patch) | |
| tree | 397052adc7965b385e628f13fd87862fa424a4b3 /kernel/rcu | |
| parent | f8ce622ac9d89260595e26d4e0da8cb6b4a8e030 (diff) | |
| download | lwn-9407f5c3ec10c155aae61fc4496a7c17a96907b4.tar.gz lwn-9407f5c3ec10c155aae61fc4496a7c17a96907b4.zip | |
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 <Neeraj.Upadhyay@amd.com>
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 <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/srcutree.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index a381b553cdca..5e2e53464794 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -712,11 +712,10 @@ void cleanup_srcu_struct(struct srcu_struct *ssp) } EXPORT_SYMBOL_GPL(cleanup_srcu_struct); -#ifdef CONFIG_PROVE_RCU /* * Check for consistent reader flavor. */ -void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) +void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) { int old_read_flavor; struct srcu_data *sdp; @@ -734,8 +733,7 @@ void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) } WARN_ONCE(old_read_flavor != read_flavor, "CPU %d old state %d new state %d\n", sdp->cpu, old_read_flavor, read_flavor); } -EXPORT_SYMBOL_GPL(srcu_check_read_flavor); -#endif /* CONFIG_PROVE_RCU */ +EXPORT_SYMBOL_GPL(__srcu_check_read_flavor); /* * Counts the new reader in the appropriate per-CPU element of the |