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 > > > 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