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rcu: IPI all CPUs at GP start for strict GPs

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Currently, each CPU discovers the beginning of a given grace period
on its own time, which is again good for efficiency but bad for fast
grace periods.  This commit therefore uses on_each_cpu() to IPI each
CPU after grace-period initialization in order to inform each CPU of
the new grace period in a timely manner, but only in kernels build with
CONFIG_RCU_STRICT_GRACE_PERIOD=y.

Reported-by Jann Horn <jannh@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2020-08-06 19:21:48 -07:00
parent 1a2f5d57a3
commit 933ada2c33
1 changed files with 13 additions and 0 deletions
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13
kernel/rcu/tree.c
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@ -1695,6 +1695,15 @@ static void rcu_gp_torture_wait(void)
} }
} }
/*
* Handler for on_each_cpu() to invoke the target CPU's RCU core
* processing.
*/
static void rcu_strict_gp_boundary(void *unused)
{
invoke_rcu_core();
}
/* /*
* Initialize a new grace period. Return false if no grace period required. * Initialize a new grace period. Return false if no grace period required.
*/ */
@ -1823,6 +1832,10 @@ static bool rcu_gp_init(void)
WRITE_ONCE(rcu_state.gp_activity, jiffies); WRITE_ONCE(rcu_state.gp_activity, jiffies);
} }
// If strict, make all CPUs aware of new grace period.
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
return true; return true;
} }