diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-10-02 16:54:49 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-11-27 08:40:09 -0800 |
| commit | 2e672ab2d491713541963afca3a5967ccc2376e9 (patch) | |
| tree | bb47329042e035fbda4b6e8140d51075851c3982 | |
| parent | 4fbd8d194f06c8a3fd2af1ce560ddb31f7ec8323 (diff) | |
rcu: Avoid ->dynticks_nmi_nesting store tearing
NMIs can nest, and store tearing could in theory happen on carries
from one byte to the next. This commit therefore adds the WRITE_ONCE()
macros preventing this.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| -rw-r--r-- | kernel/rcu/tree.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f9c0ca2ccf0c..c5d960f86cf8 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1103,7 +1103,8 @@ void rcu_nmi_enter(void) rcu_dynticks_eqs_exit(); incby = 1; } - rdtp->dynticks_nmi_nesting += incby; + WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* Prevent store tearing. */ + rdtp->dynticks_nmi_nesting + incby); barrier(); } @@ -1135,12 +1136,13 @@ void rcu_nmi_exit(void) * leave it in non-RCU-idle state. */ if (rdtp->dynticks_nmi_nesting != 1) { - rdtp->dynticks_nmi_nesting -= 2; + WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* No store tearing. */ + rdtp->dynticks_nmi_nesting - 2); return; } /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ - rdtp->dynticks_nmi_nesting = 0; + WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ rcu_dynticks_eqs_enter(); } |