svn commit: r347183 - head/sys/geom

[Kyle Evans]

On Mon, May 6, 2019 at 4:48 AM Roger Pau Monné <royger at freebsd.org> wrote:
>
> Author: royger
> Date: Mon May  6 09:48:34 2019
> New Revision: 347183
> URL: https://svnweb.freebsd.org/changeset/base/347183
>
> Log:
>   geom: fix initialization order
>
>   There's a race between the initialization of devsoftc.mtx (by devinit)
>   and the creation of the geom worker thread g_run_events, which calls
>   devctl_queue_data_f. Both of those are initialized at SI_SUB_DRIVERS
>   and SI_ORDER_FIRST, which means the geom worked thread can be created
>   before the mutex has been initialized, leading to the panic below:
>
>    wpanic: mtx_lock() of spin mutex (null) @ /usr/home/osstest/build.135317.build-amd64-freebsd/freebsd/sys/kern/subr_bus.c:620
>    cpuid = 3
>    time = 1
>    KDB: stack backtrace:
>    db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe003b968710
>    vpanic() at vpanic+0x19d/frame 0xfffffe003b968760
>    panic() at panic+0x43/frame 0xfffffe003b9687c0
>    __mtx_lock_flags() at __mtx_lock_flags+0x145/frame 0xfffffe003b968810
>    devctl_queue_data_f() at devctl_queue_data_f+0x6a/frame 0xfffffe003b968840
>    g_dev_taste() at g_dev_taste+0x463/frame 0xfffffe003b968a00
>    g_load_class() at g_load_class+0x1bc/frame 0xfffffe003b968a30
>    g_run_events() at g_run_events+0x197/frame 0xfffffe003b968a70
>    fork_exit() at fork_exit+0x84/frame 0xfffffe003b968ab0
>    fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe003b968ab0
>    --- trap 0, rip = 0, rsp = 0, rbp = 0 ---
>    KDB: enter: panic
>    [ thread pid 13 tid 100029 ]
>    Stopped at      kdb_enter+0x3b: movq    $0,kdb_why
>
>   Fix this by initializing geom at SI_ORDER_SECOND instead of
>   SI_ORDER_FIRST.
>
>   Sponsored by:         Citrix Systems R&D
>   Reviewed by:          kevans, markj
>   Differential revision:        https://reviews.freebsd.org/D20148
>

Hi,

Any objections to my MFC'ing this on ~Thursday with the tun change
that sparked it?

Thanks,

Kyle Evans