On 04/05/2017 02:48 PM, Jan Kiszka wrote: > On 2017-04-05 13:43, Måns Rullgård wrote: >> Ralf Ramsauer <[email protected]> writes: >> >>> Hi, >>> >>> I need spinlocks in inmates on ARM, so I simply included asm/spinlock.h. >>> Taking locks in inmates on ARM somehow doesn't work at all, but that's >>> not the main issue. As soon as I try to take locks, cells can not be >>> destroyed any longer, the whole system freezes on cell destroy. >>> >>> I was able to trace this down to the 'ldrex' instruction. This minimal >>> example triggers this behavior (tested on a TK1, can not test it on >>> other boards): >>> >>> #include <inmate.h> >>> >>> void inmate_main(void) >>> { >>> unsigned int foo = 0, bar = 0; >>> >>> printk("Foo!\n"); >>> asm volatile("ldrex %0, [%1]\n\t" >>> : "=&r" (foo) : "r" (bar)); >>> >>> printk("Bar!\n"); >>> while(1); >>> asm volatile("wfi"); >>> } >>> >>> The example code successfully finishes, I can read Foo and Bar on my >>> serial console. But I am not able to destroy the cell afterwards. My >>> system completely hangs on "jailhouse cell destroy". >>> >>> Curiously the cell can be re-loaded and started over again. Leaving out >>> the ldrex instruction does not trigger the bug. >>> >>> - How can ldrex prevent my cell from being destroyed? >>> >>> Does it change some 'internal state' where jailhouse is not aware >>> about? > > Is your inmate opting-out from the Comm Region protocol > (JAILHOUSE_CELL_PASSIVE_COMMREG)? Yes I'm using the Jailhouse's TK1 default config. > >>> >>> - Why do spinlocks not work at all in inmates? >>> >>> spin_lock(&lock) never returns in inmates on a fresh spin lock. >>> Does the ARM implementation of spinlocks require some special >>> global initialisation that I don't know of? >> >> Spinlocks use ldrex/strex pairs, so if ldrex is broken, I wouldn't >> expect spinlocks to work either. >> > > ...and Linux use them heavily. All our ARM SMP Linux inmates would be > broken then. There must be more involved. Yes, true.
I just reanimated my Orange Pi zero and cross-checked the behaviour there: It just prints the "Foo!", no bar, and I'm able to destroy its cell afterwards. Jetson TK1 behaves different and freezes. Ralf > > Jan > -- You received this message because you are subscribed to the Google Groups "Jailhouse" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
