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rcu: Invoke rcu_spawn_core_kthreads() from rcu_spawn_gp_kthread()

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[ Upstream commit 8e4b1d2bc1 ]

Currently, rcu_spawn_core_kthreads() is invoked via an early_initcall(),
which works, except that rcu_spawn_gp_kthread() is also invoked via an
early_initcall() and rcu_spawn_core_kthreads() relies on adjustments to
kthread_prio that are carried out by rcu_spawn_gp_kthread().  There is
no guaranttee of ordering among early_initcall() handlers, and thus no
guarantee that kthread_prio will be properly checked and range-limited
at the time that rcu_spawn_core_kthreads() needs it.

In most cases, this bug is harmless.  After all, the only reason that
rcu_spawn_gp_kthread() adjusts the value of kthread_prio is if the user
specified a nonsensical value for this boot parameter, which experience
indicates is rare.

Nevertheless, a bug is a bug.  This commit therefore causes the
rcu_spawn_core_kthreads() function to be invoked directly from
rcu_spawn_gp_kthread() after any needed adjustments to kthread_prio have
been carried out.

Fixes: 48d07c04b4 ("rcu: Enable elimination of Tree-RCU softirq processing")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Paul E. McKenney
2021-03-31 10:59:05 -07:00
committed by Greg Kroah-Hartman
parent 66111dfe22
commit 728f23e53c
1 changed files with 1 additions and 1 deletions
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2
kernel/rcu/tree.c
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@@ -2837,7 +2837,6 @@ static int __init rcu_spawn_core_kthreads(void)
"%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__); "%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__);
return 0; return 0;
} }
early_initcall(rcu_spawn_core_kthreads);
/* /*
* Handle any core-RCU processing required by a call_rcu() invocation. * Handle any core-RCU processing required by a call_rcu() invocation.
@@ -4273,6 +4272,7 @@ static int __init rcu_spawn_gp_kthread(void)
wake_up_process(t); wake_up_process(t);
rcu_spawn_nocb_kthreads(); rcu_spawn_nocb_kthreads();
rcu_spawn_boost_kthreads(); rcu_spawn_boost_kthreads();
rcu_spawn_core_kthreads();
return 0; return 0;
} }
early_initcall(rcu_spawn_gp_kthread); early_initcall(rcu_spawn_gp_kthread);