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rcu: Mark rcu_state.gp_seq to detect concurrent writes

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The rcu_state structure's gp_seq field is only to be modified by the RCU
grace-period kthread, which is single-threaded.  This commit therefore
enlists KCSAN's help in enforcing this restriction.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2020-02-10 09:58:37 -08:00
parent 3d05031ae6
commit 0f11ad323d
1 changed files with 8 additions and 14 deletions
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22
kernel/rcu/tree.c
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@ -1209,7 +1209,7 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread"));
goto unlock_out;
}
trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("newreq"));
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("newreq"));
ret = true; /* Caller must wake GP kthread. */
unlock_out:
/* Push furthest requested GP to leaf node and rcu_data structure. */
@ -1657,8 +1657,7 @@ static void rcu_gp_fqs_loop(void)
WRITE_ONCE(rcu_state.jiffies_kick_kthreads,
jiffies + (j ? 3 * j : 2));
}
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqswait"));
rcu_state.gp_state = RCU_GP_WAIT_FQS;
ret = swait_event_idle_timeout_exclusive(
@ -1672,13 +1671,11 @@ static void rcu_gp_fqs_loop(void)
/* If time for quiescent-state forcing, do it. */
if (ULONG_CMP_GE(jiffies, rcu_state.jiffies_force_qs) ||
(gf & RCU_GP_FLAG_FQS)) {
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqsstart"));
rcu_gp_fqs(first_gp_fqs);
first_gp_fqs = false;
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqsend"));
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rcu_state.gp_activity, jiffies);
@ -1689,8 +1686,7 @@ static void rcu_gp_fqs_loop(void)
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rcu_state.gp_activity, jiffies);
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqswaitsig"));
ret = 1; /* Keep old FQS timing. */
j = jiffies;
@ -1782,7 +1778,7 @@ static void rcu_gp_cleanup(void)
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
rcu_state.gp_seq,
TPS("newreq"));
} else {
WRITE_ONCE(rcu_state.gp_flags,
@ -1801,8 +1797,7 @@ static int __noreturn rcu_gp_kthread(void *unused)
/* Handle grace-period start. */
for (;;) {
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("reqwait"));
rcu_state.gp_state = RCU_GP_WAIT_GPS;
swait_event_idle_exclusive(rcu_state.gp_wq,
@ -1815,8 +1810,7 @@ static int __noreturn rcu_gp_kthread(void *unused)
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rcu_state.gp_activity, jiffies);
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("reqwaitsig"));
}