Hi all,
When the kernel printk too many log, the cpu is failed to come online.
The problem is this:
For example, cpu0 bring up cpu1:
a. cpu0 call cpu_up:
cpu_up()
->_cpu_up()
->__cpu_notify(CPU_UP_PREPARE)
->__cpu_up()
->boot_secondary()
# ->wait_for_completion_timeout(&cpu_running, msecs_to_jiffires(1000))
-> if (!cpu_online(cpu)) {
pr_crit("CPU%u: failed to come online\n", cpu);
ret = -EIO;
}
->cpu_notify(CPU_ONLINE)
b. cpu1 enter kernel:
secondary_start_kernel()
@ ->printk("CPU%u: Booted secondary processor\n", cpu)
* ->calibrate_delay()
->set_cpu_online()
->complete(cpu_running)
->cpumask_set_cpu()
While cpu0 run to mark #, which wait that cpu1 complete
cpu_running, and set online.
Generally, cpu0 can get it. But if the __log_buf is too large or other
threads write
it unceasing, then cpu1 come to mark @ or * in this moment. Cpu1 is busy
outputing
buffer, which cost time more than 1s, and cpu1 have not join in sched,
so cpu0 wait it timeout.
By reading printk.c, I found that can_use_console() always return
true, which be called by
console_trylock_for_printk(). Because, have_callable_console() return
ture always, if the console
driver set CON_ANYTIME flag. I think that cpu should not output the
__log_buf in coming online,
even though have_callable_console() is true.
/*
* Can we actually use the console at this time on this cpu?
*
* Console drivers may assume that per-cpu resources have
* been allocated. So unless they're explicitly marked as
* being able to cope (CON_ANYTIME) don't call them until
* this CPU is officially up.
*/
static inline int can_use_console(unsigned int cpu)
{
return cpu_online(cpu) || have_callable_console();
}
In can_use_console, why not is &&, but ||?
Kernel Version: 3.3.0
Arch: arm
This problem trace:
[ 1722.150286] CPU1: Booted secondary processor
[ 1722.154613] Calibrating delay loop (skipped) already calibrated this CPU
.........
[ 1725.134687] CPU1: failed to come online
.........
[ 1728.055547] ------------[ cut here ]------------
[ 1728.060219] kernel BUG at kernel/workqueue.c:3332!
[ 1728.065010] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[ 1728.070503] Modules linked in: cdc_ether rtl8150 mcs7830 qf9700 asix
usbnet mma7660 sw_keyboard gt9xx g2d_33 sunxi_csi1 gc2035 ov5640
videobuf_dma_contig videobuf_core dc_sunxi(O) pvrsrvkm(O) nand(O)
[ 1728.088474] CPU: 0 Tainted: G O (3.3.0 #9)
[ 1728.093796] PC is at trustee_thread+0x24/0x514
[ 1728.098239] LR is at trustee_thread+0x1c/0x514
[ 1728.102683] pc : [<c059c750>] lr : [<c059c748>] psr: 20000013
[ 1728.102690] sp : ec05bf68 ip : ec05bf68 fp : ec05bfb4
[ 1728.114161] r10: 00000000 r9 : 00000000 r8 : 00000000
[ 1728.119383] r7 : 00000013 r6 : c059c72c r5 : 00000001 r4 : e5e162c0
[ 1728.125906] r3 : 00000000 r2 : 00000001 r1 : ec05bf40 r0 : 00000000
[ 1728.132432] Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM
Segment kernel
[ 1728.139736] Control: 10c53c7d Table: 6e35c06a DAC: 00000015
.........
[ 1728.709566] Process workqueue_trust (pid: 22196, stack limit =
0xec05a2f8)
[ 1728.716436] Stack: (0xec05bf68 to 0xec05c000)
[ 1728.720796] bf60: c05a6c3c c007f98c c07ed100
c07ed100 c05a788c ed089de0
[ 1728.728973] bf80: e5e162c0 c059c72c 00000013 ed089de0 e5e162c0
c059c72c 00000013 00000000
[ 1728.737148] bfa0: 00000000 00000000 ec05bff4 ec05bfb8 c00732fc
c059c738 00000000 00000000
[ 1728.745324] bfc0: e5e162c0 00000000 00000000 00000000 ec05bfd0
ec05bfd0 00000000 ed089de0
[ 1728.753501] bfe0: c0073260 c0057d50 00000000 ec05bff8 c0057d50
c007326c 00d851b1 da280100
[ 1728.761669] Backtrace:
[ 1728.764140] [<c059c72c>] (trustee_thread+0x0/0x514) from [<c00732fc>]
(kthread+0x9c/0xa8)
[ 1728.772321] [<c0073260>] (kthread+0x0/0xa8) from [<c0057d50>]
(do_exit+0x0/0x764)
[ 1728.779797] r6:c0057d50 r5:c0073260 r4:ed089de0
[ 1728.784457] Code: e1a04000 ebf36dbd e1550000 0a000000 (e7f001f2)
[ 1729.130494] ---[ end trace 3deba094f67f9e11 ]---
[ 1729.140018] Kernel panic - not syncing: Fatal exception
[ 1730.355119] SMP: failed to stop secondary CPUs
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