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srcu: Apply *_ONCE() to ->srcu_last_gp_end

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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: syzbot+08f3e9d26e5541e1ecf2@syzkaller.appspotmail.com
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2019-11-04 08:08:30 -08:00
parent 7441e7661d
commit 844a378de3
1 changed files with 4 additions and 3 deletions
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7
kernel/rcu/srcutree.c
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@ -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. */