Commit 844a378d authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

srcu: Apply *_ONCE() to ->srcu_last_gp_end 



The ->srcu_last_gp_end field is accessed from any CPU at any time
by synchronize_srcu(), so non-initialization references need to use
READ_ONCE() and WRITE_ONCE().  This commit therefore makes that change.

Reported-by: default avatar <syzbot+08f3e9d26e5541e1ecf2@syzkaller.appspotmail.com>
Acked-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 7441e766

kernel/rcu/srcutree.c

+4 −3
Original line number Diff line number Diff line
@@ -530,7 +530,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) 
	idx = rcu_seq_state(ssp->srcu_gp_seq);

	WARN_ON_ONCE(idx != SRCU_STATE_SCAN2);

	cbdelay = srcu_get_delay(ssp);

	ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();

	WRITE_ONCE(ssp->srcu_last_gp_end, ktime_get_mono_fast_ns());

	rcu_seq_end(&ssp->srcu_gp_seq);

	gpseq = rcu_seq_current(&ssp->srcu_gp_seq);

	if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, gpseq))
@@ -762,6 +762,7 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp) 
	unsigned long flags;

	struct srcu_data *sdp;

	unsigned long t;

	unsigned long tlast;



	/* If the local srcu_data structure has callbacks, not idle.  */

	local_irq_save(flags);
@@ -780,9 +781,9 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp) 


	/* First, see if enough time has passed since the last GP. */

	t = ktime_get_mono_fast_ns();

	tlast = READ_ONCE(ssp->srcu_last_gp_end);

	if (exp_holdoff == 0 ||

	    time_in_range_open(t, ssp->srcu_last_gp_end,

			       ssp->srcu_last_gp_end + exp_holdoff))

	    time_in_range_open(t, tlast, tlast + exp_holdoff))

		return false; /* Too soon after last GP. */



	/* Next, check for probable idleness. */

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