samsung_sm8750/android_kernel_samsung_sm8750
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

rcu: handle unstable rdp in rcu_read_unlock_strict()

Browse Source 
[ Upstream commit fcf0e25ad4c8d14d2faab4d9a17040f31efce205 ]

rcu_read_unlock_strict() can be called with preemption enabled
which can make for an unstable rdp and a racy norm value.

Fix this by dropping the preempt-count in __rcu_read_unlock()
after the call to rcu_read_unlock_strict(), adjusting the
preempt-count check appropriately.

Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Ankur Arora
2024-12-12 20:06:55 -08:00
committed by Greg Kroah-Hartman
parent 4a36d93a01
commit 9abec90c85
2 changed files with 11 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/rcupdate.h
View File

@@ -97,9 +97,9 @@ static inline void __rcu_read_lock(void)
static inline void __rcu_read_unlock(void) static inline void __rcu_read_unlock(void)
{ {
preempt_enable();
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
rcu_read_unlock_strict(); rcu_read_unlock_strict();
preempt_enable();
} }
static inline int rcu_preempt_depth(void) static inline int rcu_preempt_depth(void)

11
kernel/rcu/tree_plugin.h
View File

@@ -821,8 +821,17 @@ void rcu_read_unlock_strict(void)
{ {
struct rcu_data *rdp; struct rcu_data *rdp;
if (irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) if (irqs_disabled() || in_atomic_preempt_off() || !rcu_state.gp_kthread)
return; return;
/*
* rcu_report_qs_rdp() can only be invoked with a stable rdp and
* from the local CPU.
*
* The in_atomic_preempt_off() check ensures that we come here holding
* the last preempt_count (which will get dropped once we return to
* __rcu_read_unlock().
*/
rdp = this_cpu_ptr(&rcu_data); rdp = this_cpu_ptr(&rcu_data);
rdp->cpu_no_qs.b.norm = false; rdp->cpu_no_qs.b.norm = false;
rcu_report_qs_rdp(rdp); rcu_report_qs_rdp(rdp);