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Groups > linux.kernel > #1225419
| From | Paolo Bonzini <pbonzini@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm |
| Date | 2015-09-15 18:50 +0200 |
| Message-ID | <q91AE-24K-45@gated-at.bofh.it> (permalink) |
| References | <q8XdE-4lR-29@gated-at.bofh.it> <q8Y9K-5HB-47@gated-at.bofh.it> <q8YCL-6fP-49@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 15/09/2015 15:36, Christian Borntraeger wrote: > I am wondering why the old code behaved in such fatal ways. Is there > some interaction between waiting for a reschedule in the > synchronize_sched writer and some fork code actually waiting for the > read side to get the lock together with some rescheduling going on > waiting for a lock that fork holds? lockdep does not give me an hints > so I have no clue :-( It may just be consuming too much CPU usage. kernel/rcu/tree.c warns about it: * if you are using synchronize_sched_expedited() in a loop, please * restructure your code to batch your updates, and then use a single * synchronize_sched() instead. and you may remember that in KVM we switched from RCU to SRCU exactly to avoid userspace-controlled synchronize_rcu_expedited(). In fact, I would say that any userspace-controlled call to *_expedited() is a bug waiting to happen and a bad idea---because userspace can, with little effort, end up calling it in a loop. Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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[4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-15 14:10 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Peter Zijlstra <peterz@infradead.org> - 2015-09-15 15:10 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-15 15:40 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Tejun Heo <tj@kernel.org> - 2015-09-15 16:00 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Paolo Bonzini <pbonzini@redhat.com> - 2015-09-15 18:50 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-15 19:40 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Paolo Bonzini <pbonzini@redhat.com> - 2015-09-16 10:40 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-16 11:00 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Paolo Bonzini <pbonzini@redhat.com> - 2015-09-16 11:20 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Oleg Nesterov <oleg@redhat.com> - 2015-09-16 14:30 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Paolo Bonzini <pbonzini@redhat.com> - 2015-09-16 14:40 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Oleg Nesterov <oleg@redhat.com> - 2015-09-16 14:50 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-16 15:00 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Tejun Heo <tj@kernel.org> - 2015-09-16 16:20 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Paolo Bonzini <pbonzini@redhat.com> - 2015-09-16 16:20 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-15 23:20 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Tejun Heo <tj@kernel.org> - 2015-09-15 23:30 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-15 23:40 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Tejun Heo <tj@kernel.org> - 2015-09-16 00:30 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-16 01:40 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Tejun Heo <tj@kernel.org> - 2015-09-16 03:30 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-16 06:40 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Tejun Heo <tj@kernel.org> - 2015-09-16 13:10 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-16 09:50 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-16 13:00 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Tejun Heo <tj@kernel.org> - 2015-09-16 13:10 +0200
Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-16 14:00 +0200
[PATCH cgroup/for-4.3-fixes 1/2] Revert "cgroup: simplify threadgroup locking" Tejun Heo <tj@kernel.org> - 2015-09-16 18:00 +0200
[PATCH cgroup/for-4.3-fixes 2/2] Revert "sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem" Tejun Heo <tj@kernel.org> - 2015-09-16 18:00 +0200
Re: [PATCH cgroup/for-4.3-fixes 1/2] Revert "cgroup: simplify threadgroup locking" Oleg Nesterov <oleg@redhat.com> - 2015-09-16 19:10 +0200
Re: [PATCH cgroup/for-4.3-fixes 1/2] Revert "cgroup: simplify threadgroup locking" Christian Borntraeger <borntraeger@de.ibm.com> - 2015-09-16 20:50 +0200
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