lkml.org 
[lkml]   [2020]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.4 32/91] arm64: smp: fix smp_send_stop() behaviour
    Date
    From: Cristian Marussi <cristian.marussi@arm.com>

    commit d0bab0c39e32d39a8c5cddca72e5b4a3059fe050 upstream.

    On a system with only one CPU online, when another one CPU panics while
    starting-up, smp_send_stop() will fail to send any STOP message to the
    other already online core, resulting in a system still responsive and
    alive at the end of the panic procedure.

    [ 186.700083] CPU3: shutdown
    [ 187.075462] CPU2: shutdown
    [ 187.162869] CPU1: shutdown
    [ 188.689998] ------------[ cut here ]------------
    [ 188.691645] kernel BUG at arch/arm64/kernel/cpufeature.c:886!
    [ 188.692079] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
    [ 188.692444] Modules linked in:
    [ 188.693031] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.6.0-rc4-00001-g338d25c35a98 #104
    [ 188.693175] Hardware name: Foundation-v8A (DT)
    [ 188.693492] pstate: 200001c5 (nzCv dAIF -PAN -UAO)
    [ 188.694183] pc : has_cpuid_feature+0xf0/0x348
    [ 188.694311] lr : verify_local_elf_hwcaps+0x84/0xe8
    [ 188.694410] sp : ffff800011b1bf60
    [ 188.694536] x29: ffff800011b1bf60 x28: 0000000000000000
    [ 188.694707] x27: 0000000000000000 x26: 0000000000000000
    [ 188.694801] x25: 0000000000000000 x24: ffff80001189a25c
    [ 188.694905] x23: 0000000000000000 x22: 0000000000000000
    [ 188.694996] x21: ffff8000114aa018 x20: ffff800011156a38
    [ 188.695089] x19: ffff800010c944a0 x18: 0000000000000004
    [ 188.695187] x17: 0000000000000000 x16: 0000000000000000
    [ 188.695280] x15: 0000249dbde5431e x14: 0262cbe497efa1fa
    [ 188.695371] x13: 0000000000000002 x12: 0000000000002592
    [ 188.695472] x11: 0000000000000080 x10: 00400032b5503510
    [ 188.695572] x9 : 0000000000000000 x8 : ffff800010c80204
    [ 188.695659] x7 : 00000000410fd0f0 x6 : 0000000000000001
    [ 188.695750] x5 : 00000000410fd0f0 x4 : 0000000000000000
    [ 188.695836] x3 : 0000000000000000 x2 : ffff8000100939d8
    [ 188.695919] x1 : 0000000000180420 x0 : 0000000000180480
    [ 188.696253] Call trace:
    [ 188.696410] has_cpuid_feature+0xf0/0x348
    [ 188.696504] verify_local_elf_hwcaps+0x84/0xe8
    [ 188.696591] check_local_cpu_capabilities+0x44/0x128
    [ 188.696666] secondary_start_kernel+0xf4/0x188
    [ 188.697150] Code: 52805001 72a00301 6b01001f 54000ec0 (d4210000)
    [ 188.698639] ---[ end trace 3f12ca47652f7b72 ]---
    [ 188.699160] Kernel panic - not syncing: Attempted to kill the idle task!
    [ 188.699546] Kernel Offset: disabled
    [ 188.699828] CPU features: 0x00004,20c02008
    [ 188.700012] Memory Limit: none
    [ 188.700538] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---

    [root@arch ~]# echo Helo
    Helo
    [root@arch ~]# cat /proc/cpuinfo | grep proce
    processor : 0

    Make smp_send_stop() account also for the online status of the calling CPU
    while evaluating how many CPUs are effectively online: this way, the right
    number of STOPs is sent, so enforcing a proper freeze of the system at the
    end of panic even under the above conditions.

    Fixes: 08e875c16a16c ("arm64: SMP support")
    Reported-by: Dave Martin <Dave.Martin@arm.com>
    Acked-by: Mark Rutland <mark.rutland@arm.com>
    Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
    Signed-off-by: Will Deacon <will@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/arm64/kernel/smp.c | 17 ++++++++++++++---
    1 file changed, 14 insertions(+), 3 deletions(-)

    --- a/arch/arm64/kernel/smp.c
    +++ b/arch/arm64/kernel/smp.c
    @@ -769,11 +769,22 @@ void tick_broadcast(const struct cpumask
    }
    #endif

    +/*
    + * The number of CPUs online, not counting this CPU (which may not be
    + * fully online and so not counted in num_online_cpus()).
    + */
    +static inline unsigned int num_other_online_cpus(void)
    +{
    + unsigned int this_cpu_online = cpu_online(smp_processor_id());
    +
    + return num_online_cpus() - this_cpu_online;
    +}
    +
    void smp_send_stop(void)
    {
    unsigned long timeout;

    - if (num_online_cpus() > 1) {
    + if (num_other_online_cpus()) {
    cpumask_t mask;

    cpumask_copy(&mask, cpu_online_mask);
    @@ -784,10 +795,10 @@ void smp_send_stop(void)

    /* Wait up to one second for other CPUs to stop */
    timeout = USEC_PER_SEC;
    - while (num_online_cpus() > 1 && timeout--)
    + while (num_other_online_cpus() && timeout--)
    udelay(1);

    - if (num_online_cpus() > 1)
    + if (num_other_online_cpus())
    pr_warning("SMP: failed to stop secondary CPUs\n");
    }


    \
     
     \ /
      Last update: 2020-04-01 18:31    [W:3.980 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site