Hi Juergen, If you are willing to do the patch I think it will be faster to being accepted, what about the BUG_ON(…) in evtchn_2l_unmask from events_2l.c file?
Cheers, Luca > On 18 Mar 2021, at 07:54, Jürgen Groß <jgr...@suse.com> wrote: > > On 17.03.21 15:32, Luca Fancellu wrote: >> Hi all, >> we've been encountering an issue when using the kernel 5.10 with preempt_rt >> support for Dom0, the problem is that during the boot of Dom0, it hits a >> BUG_ON(!irqs_disabled()) from the function evtchn_fifo_unmask defined in >> events_fifo.c. >> This is the call stack: >> [ 17.817018] ------------[ cut here ]------------ >> [ 17.817021] kernel BUG at drivers/xen/events/events_fifo.c:258! >> [ 18.817079] Internal error: Oops - BUG: 0 [#1] PREEMPT_RT SMP >> [ 18.817081] Modules linked in: bridge stp llc ipv6 >> [ 18.817086] CPU: 3 PID: 558 Comm: xenstored Not tainted >> 5.10.16-rt25-yocto-preempt-rt #1 >> [ 18.817089] Hardware name: Arm Neoverse N1 System Development Platform >> (DT) >> [ 18.817090] pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--) >> [ 18.817092] pc : evtchn_fifo_unmask+0xd4/0xe0 >> [ 18.817099] lr : xen_irq_lateeoi_locked+0xec/0x200 >> [ 18.817102] sp : ffff8000123f3cc0 >> [ 18.817102] x29: ffff8000123f3cc0 x28: ffff0000427b1d80 >> [ 18.817104] x27: 0000000000000000 x26: 0000000000000000 >> [ 18.817106] x25: 0000000000000001 x24: 0000000000000001 >> [ 18.817107] x23: ffff0000412fc900 x22: 0000000000000004 >> [ 18.817109] x21: 0000000000000000 x20: ffff000042e06990 >> [ 18.817110] x19: ffff0000427b1d80 x18: 0000000000000010 >> [ 18.817112] x17: 0000000000000000 x16: 0000000000000000 >> [ 18.817113] x15: 0000000000000002 x14: 0000000000000001 >> [ 18.817114] x13: 000000000001a7e8 x12: 0000000000000040 >> [ 18.817116] x11: ffff000040400248 x10: ffff00004040024a >> [ 18.817117] x9 : ffff800011be5200 x8 : ffff000040400270 >> [ 18.817119] x7 : 0000000000000000 x6 : 0000000000000003 >> [ 18.817120] x5 : 0000000000000000 x4 : ffff000040400308 >> [ 18.817121] x3 : ffff0000408a400c x2 : 0000000000000000 >> [ 18.817122] x1 : 0000000000000000 x0 : ffff0000408a4000 >> [ 18.817124] Call trace: >> [ 18.817125] evtchn_fifo_unmask+0xd4/0xe0 >> [ 18.817127] xen_irq_lateeoi_locked+0xec/0x200 >> [ 18.817129] xen_irq_lateeoi+0x48/0x64 >> [ 18.817131] evtchn_write+0x124/0x15c >> [ 18.817134] vfs_write+0xf0/0x2cc >> [ 18.817137] ksys_write+0xe0/0x100 >> [ 18.817139] __arm64_sys_write+0x20/0x30 >> [ 18.817142] el0_svc_common.constprop.0+0x78/0x1a0 >> [ 18.817145] do_el0_svc+0x24/0x90 >> [ 18.817147] el0_svc+0x14/0x20 >> [ 18.817151] el0_sync_handler+0x1a4/0x1b0 >> [ 18.817153] el0_sync+0x174/0x180 >> [ 18.817156] Code: 52800120 b90023e6 97e6d104 17fffff0 (d4210000) >> [ 18.817158] ---[ end trace 0000000000000002 ]--- >> Our last tested kernel was the 5.4 and our analysis pointed out that the >> introduction of the lateeoi framework (xen/events: add a new "late EOI" >> evtchn framework) in conjunction with the preempt_rt patches (irqs kept >> enabled between spinlock_t/rwlock_t _irqsave///_irqrestore operations) is >> the root cause. >> Given that many modifications were made to the mask/unmask operations, a big >> one from Juergen Gross (xen/events: don't unmask an event channel when an >> eoi is pending), is the BUG_ON(...) still needed? >> With the mentioned commit every call to a mask/unmask operation is protected >> by a spinlock, so I would like to have some feedbacks from who has more >> experience than me on this part of the code. > > I think this BUG_ON() can be removed. > > Are you planning to send a patch? > > > Juergen > <OpenPGP_0xB0DE9DD628BF132F.asc>
