Urgent RCU pull request for v6.1
This pull request contains a commit that fixes bf95b2bc3e42 ("rcu: Switch
polled grace-period APIs to ->gp_seq_polled"), which could incorrectly
leave interrupts enabled after an early-boot call to synchronize_rcu().
Such synchronize_rcu() calls must acquire leaf rcu_node locks in order to
properly interact with polled grace periods, but the code did not take
into account the possibility of synchronize_rcu() being invoked from
the portion of the boot sequence during which interrupts are disabled.
This commit therefore switches the lock acquisition and release from
irq to irqsave/irqrestore.
rcu: Keep synchronize_rcu() from enabling irqs in early boot
Making polled RCU grace periods account for expedited grace periods
required acquiring the leaf rcu_node structure's lock during early boot,
but after rcu_init() was called. This lock is irq-disabled, but the
code incorrectly assumes that irqs are always disabled when invoking
synchronize_rcu(). The exception is early boot before the scheduler has
started, which means that upon return from synchronize_rcu(), irqs will
be incorrectly enabled.
This commit fixes this bug by using irqsave/irqrestore locking primitives.
Fixes: bf95b2bc3e42 ("rcu: Switch polled grace-period APIs to ->gp_seq_polled")
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
1 file changed
