Commit 36f65f1d authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

srcu: Check for consistent global per-srcu_struct NMI safety 

This commit adds runtime checks to verify that a given srcu_struct uses
consistent NMI-safe (or not) read-side primitives globally, but based
on the per-CPU data.  These global checks are made by the grace-period
code that must scan the srcu_data structures anyway, and are done only
in kernels built with CONFIG_PROVE_RCU=y.

Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/



Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
parent 27120e7d

kernel/rcu/srcutree.c

+5 −0
Original line number Diff line number Diff line
@@ -429,13 +429,18 @@ static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int idx) 
static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx)

{

	int cpu;

	unsigned long mask = 0;

	unsigned long sum = 0;



	for_each_possible_cpu(cpu) {

		struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu);



		sum += atomic_long_read(&cpuc->srcu_unlock_count[idx]);

		if (IS_ENABLED(CONFIG_PROVE_RCU))

			mask = mask | READ_ONCE(cpuc->srcu_nmi_safety);

	}

	WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask >> 1)),

		  "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp);

	return sum;

}