Peter,
What's your opinion about the patch? We hit it when enabling Medfield Android
mobile.
This patch would put AP to a loop.
Another method to fix it is just to enlarge the wait time, for example, from
2HZ to 10HZ.
Yanmin
-------- Forwarded Message --------
> From: Chen, LinX Z <linx.z.c...@intel.com>
> To: linux-kernel@vger.kernel.org
> Cc: mi...@redhat.com, t...@linutronix.de, h...@zytor.com,
> yanmin_zh...@linux.intel.com
> Subject: [PATCH] x86/smp: Fix cpuN startup panic
> Date: Tue, 07 Aug 2012 18:50:40 +0900
>
> From: Lin Chen <linx.z.c...@intel.com>
>
> We hit a panic while doing cpu hotplug test.
> <0>[ 627.982857] Kernel panic - not syncing: smp_callin: CPU1 started up but
> did not get a callout!
> <0>[ 627.982864]
> <4>[ 627.982876] Pid: 0, comm: kworker/0:1 Tainted: G ...
> <4>[ 627.982883] Call Trace:
> <4>[ 627.982903] [<c18f2977>] panic+0x66/0x16c
> <4>[ 627.982918] [<c12234cc>] ? default_get_apic_id+0x1c/0x40
> <4>[ 627.982931] [<c18ef96d>] start_secondary+0xda/0x252
>
> During BSP bootup AP, it is possible that BSP be preempted before
> finishing STARTUP sequence of AP(set cpu_callout_mask) which maybe cause
> AP busy wait for it. At present, AP will wait for 2 seconds then panic.
>
> This patch let AP waits until BSP finish the startup sequence and gives
> WARNING when BSP is preempted more than 2 seconds.
>
> Signed-off-by: Yanmin Zhang <yanmin_zh...@linux.intel.com>
> Signed-off-by: Lin Chen <linx.z.c...@intel.com>
> ---
> arch/x86/kernel/smpboot.c | 11 ++++++-----
> 1 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 7c5a8c3..a9e3379 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -165,19 +165,20 @@ static void __cpuinit smp_callin(void)
> * Waiting 2s total for startup (udelay is not yet working)
> */
> timeout = jiffies + 2*HZ;
> - while (time_before(jiffies, timeout)) {
> + while (1) {
> /*
> * Has the boot CPU finished it's STARTUP sequence?
> */
> if (cpumask_test_cpu(cpuid, cpu_callout_mask))
> break;
> cpu_relax();
> + if (!time_before(jiffies, timeout)) {
> + WARN(1, "%s: CPU%d started up but did not get a
> callout!\n",
> + __func__, cpuid);
> + timeout = jiffies + 2*HZ;
> + }
> }
>
> - if (!time_before(jiffies, timeout)) {
> - panic("%s: CPU%d started up but did not get a callout!\n",
> - __func__, cpuid);
> - }
>
> /*
> * the boot CPU has finished the init stage and is spinning
> --
> 1.7.1
--
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