On 27.03.20 00:24, Igor Druzhinin wrote:
On 26/03/2020 09:19, Juergen Gross wrote:Some keyhandlers are calling process_pending_softirqs() while holding a rcu_read_lock(). This is wrong, as process_pending_softirqs() might activate rcu calls which should not happen inside a rcu_read_lock().For that purpose modify process_pending_softirqs() to not allow rcu callback processing when a rcu_read_lock() is being held. Signed-off-by: Juergen Gross <jgr...@suse.com> Reviewed-by: Jan Beulich <jbeul...@suse.com> --- V3: - add RCU_SOFTIRQ to ignore in process_pending_softirqs_norcu() (Roger Pau Monné) V5: - block rcu processing depending on rch_read_lock() being held or not (Jan Beulich)Juergen, Our BVT revealed a likely problem with this commit in that form. Since 12509bbeb9e ("rwlocks: call preempt_disable() when taking a rwlock") preemption is disabled after taking cpu_maps which will block RCU callback processing inside rcu_barrier itself. This will result in
Why would that block RCU callback processing? RCU callbacks should be blocked only if a rcu lock is being held. Did I miss something in my patches?
all system hang on boot after 540d4d60378 ("cpu: sync any remaining
RCU callbacks before CPU up/down").
Juergen
