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| author | Paul E. McKenney <paulmck@kernel.org> | 2020-08-07 22:44:10 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-08-25 03:40:27 +0200 |
| commit | 3d29aaf1ef992b5b4612fe32b9e6f517f7bba904 (patch) | |
| tree | 5ea92127640c2899da6805a887d25c9e249c5154 /kernel/rcu | |
| parent | rcu: IPI all CPUs at GP end for strict GPs (diff) | |
| download | linux-3d29aaf1ef992b5b4612fe32b9e6f517f7bba904.tar.xz linux-3d29aaf1ef992b5b4612fe32b9e6f517f7bba904.zip | |
rcu: Provide optional RCU-reader exit delay for strict GPs
The goal of this series is to increase the probability of tools like
KASAN detecting that an RCU-protected pointer was used outside of its
RCU read-side critical section. Thus far, the approach has been to make
grace periods and callback processing happen faster. Another approach
is to delay the pointer leaker. This commit therefore allows a delay
to be applied to exit from RCU read-side critical sections.
This slowdown is specified by a new rcutree.rcu_unlock_delay kernel boot
parameter that specifies this delay in microseconds, defaulting to zero.
Reported-by Jann Horn <jannh@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index dfdb9020f136..3f3a4ffd4df2 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -430,6 +430,12 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp) return !list_empty(&rnp->blkd_tasks); } +// Add delay to rcu_read_unlock() for strict grace periods. +static int rcu_unlock_delay; +#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD +module_param(rcu_unlock_delay, int, 0444); +#endif + /* * Report deferred quiescent states. The deferral time can * be quite short, for example, in the case of the call from @@ -460,10 +466,12 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags) } t->rcu_read_unlock_special.s = 0; if (special.b.need_qs) { - if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) { rcu_report_qs_rdp(rdp->cpu, rdp); - else + udelay(rcu_unlock_delay); + } else { rcu_qs(); + } } /* |