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rcu: Make rcu_report_exp_cpu_mult() caller acquire lock

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There is a hard-to-trigger bug in the expedited grace-period computation
whose fix requires that the __sync_rcu_exp_select_node_cpus() function
to check that the grace-period sequence number has not changed before
invoking rcu_report_exp_cpu_mult().  However, this check must be done
while holding the leaf rcu_node structure's ->lock.

This commit therefore prepares for that fix by moving this lock's
acquisition from rcu_report_exp_cpu_mult() to its callers (all two
of them).

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
This commit is contained in:
Paul E. McKenney 2024-10-25 11:43:28 -07:00 committed by Uladzislau Rezki (Sony)
parent 049dfe96ba
commit d16e32f75f
1 changed files with 13 additions and 7 deletions
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20
kernel/rcu/tree_exp.h
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@ -227,16 +227,16 @@ static void __maybe_unused rcu_report_exp_rnp(struct rcu_node *rnp, bool wake)
/*
* Report expedited quiescent state for multiple CPUs, all covered by the
* specified leaf rcu_node structure.
* specified leaf rcu_node structure, which is acquired by the caller.
*/
static void rcu_report_exp_cpu_mult(struct rcu_node *rnp,
static void rcu_report_exp_cpu_mult(struct rcu_node *rnp, unsigned long flags,
unsigned long mask, bool wake)
__releases(rnp->lock)
{
int cpu;
unsigned long flags;
struct rcu_data *rdp;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
raw_lockdep_assert_held_rcu_node(rnp);
if (!(rnp->expmask & mask)) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return;
@ -257,8 +257,12 @@ static void rcu_report_exp_cpu_mult(struct rcu_node *rnp,
*/
static void rcu_report_exp_rdp(struct rcu_data *rdp)
{
unsigned long flags;
struct rcu_node *rnp = rdp->mynode;
WRITE_ONCE(rdp->cpu_no_qs.b.exp, false);
rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true);
raw_spin_lock_irqsave_rcu_node(rnp, flags);
rcu_report_exp_cpu_mult(rnp, flags, rdp->grpmask, true);
}
/* Common code for work-done checking. */
@ -432,8 +436,10 @@ retry_ipi:
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
/* Report quiescent states for those that went offline. */
if (mask_ofl_test)
rcu_report_exp_cpu_mult(rnp, mask_ofl_test, false);
if (mask_ofl_test) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
rcu_report_exp_cpu_mult(rnp, flags, mask_ofl_test, false);
}
}
static void rcu_exp_sel_wait_wake(unsigned long s);