Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 2e672ab2 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 4fbd8d19

kernel/rcu/tree.c

+5 −3
Original line number Diff line number Diff line
@@ -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();

}