On 02/25/2016 02:33 PM, Peter Hurley wrote: > On 02/25/2016 01:32 PM, Jiri Slaby wrote: >> On 02/25/2016, 09:51 PM, Linus Torvalds wrote: >>> Jiri, can you check your try_to_wake_up() disassembly for some >>> indirect "jmp" instructions? >> >> Nope, there is none. >> >> I will reply to all your questions tomorrow. >> >> Just quickly, as I have to go (and don't want you to duplicate efforts) >> the kernel which was used can be obtained here: >> https://build.opensuse.org/package/binaries/openSUSE:Factory:Staging:I/kernel-default?repository=standard >> >> The issue is very weird, indeed, this is what I noted to our bugzilla: >> The stack trace ends in call of try_to_wake_up. Then, there it has to be >> some of the indirect calls: >> >> callq *0x40(%rax) >> p->sched_class->select_task_rq from select_task_rq >> >> RAX is 0x00000000bb37e180, barely can be read with offset 0x40 >> >> callq *0xd85656(%rip) # ffffffff81e2aba0 <smp_ops+0x20> >> smp_ops.smp_send_reschedule from ttwu_queue_remote >> >> Which hardly can be it, given smp_ops is static. >> >> So it has to be some other "call *" from a nested function :(. >> >> >> >> >> Interestingly, RBP contains address inside try_to_wake_up -- >> ffffffff810a535a (dunno why) which is: >> ffffffff810a5355: e8 66 a0 ff ff callq ffffffff8109f3c0 >> <ttwu_stat> >> ffffffff810a535a: e9 9d fe ff ff jmpq ffffffff810a51fc >> <try_to_wake_up+0x3c> > > That would imply that RSP was off by +8 when the ttwu_stat() epilog was > executed so that RBP <= ret addr and RIP <= some local var in try_to_wake_up() > stack frame. > > Looks like R15 in the crash report could be what RBP should have been. > > Now to find out why RSP is +8 Which I would investigate if I could download that kernel. Unfortunately, OBS doesn't like me so if you could make that kernel available some other way or send me a mixed listing of kernel/sched/core.c >> ttwu_stat does in the begginning: >> mov $0x16e80,%r14 >> >> which is what we actually still have in r14 when it crashes. The first >> ttwu_stat's "if" has to go through the true branch (otherwise r14 would >> be overwritten). >> >> >> >> Another note: we die when jmp/calling to 0xffff88023fd40000. >> RSI=RDI=0xffff88023fdd6e80. RSI-RIP is 0x96e80, which is R14 + 0x80000. >> Coincidence? >> >> thanks, >> > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html