linux 3.10 一次softlock排查
x86架构。一个同事分析的crash，我在他基础上再次协助分析，也没有获得进展，只是记录一下分析过程。记录是指备忘，万一有人解决过，也好给我们点帮助。
有一次软锁，大多数cpu被锁，log中第一个认为被锁的cpu已经被冲掉了，直接敲入log，总共24个cpu，首先看到的是17cpu的堆栈，分析如下：
[ 4588.212690] CPU: PID: Comm: zte_uep1 Tainted: G W OEL ------------ T 3.10.-693.21..el7.x86_64 #
[ 4588.212691] Hardware name: QEMU Standard PC (i440FX + PIIX, ), BIOS rel-1.10.--g5f4c7b1-prebuilt.qemu-project.org //
[ 4588.212692] task: ffff880a3d364f10 ti: ffff880aa7fd8000 task.ti: ffff880aa7fd8000
[ 4588.212693] RIP: :[<ffffffff810fe46a>]
[ 4588.212696] [<ffffffff810fe46a>] smp_call_function_many+0x20a/0x270
[ 4588.212697] RSP: :ffff880aa7fdbcb0 EFLAGS:
[ 4588.212698] RAX: RBX: 00080000810706a0 RCX: ffff880b52b9bfa0
[ 4588.212698] RDX: RSI: RDI:
[ 4588.212699] RBP: ffff880aa7fdbce8 R08: ffff880beeb51c00 R09: ffffffff8132a699
[ 4588.212700] R10: ffff88169235abc0 R11: ffffea0057afa800 R12:
[ 4588.212701] R13: R14: ffff880aa7fdbc60 R15:
[ 4588.212702] FS: 00007fbd936f6700() GS:ffff881692340000() knlGS:
[ 4588.212703] CS: DS: ES: CR0:
[ 4588.212704] CR2: 00007fbd6c004d80 CR3: 00000015c7fa6000 CR4: 00000000001606e0
[ 4588.212706] DR0: DR1: DR2:
[ 4588.212707] DR3: DR6: 00000000ffff0ff0 DR7:
[ 4588.212707] Call Trace:
[ 4588.212708]
[ 4588.212712] [<ffffffff81070868>] native_flush_tlb_others+0xb8/0xc0
[ 4588.212712]
[ 4588.212714] [<ffffffff81070938>] flush_tlb_mm_range+0x68/0x140
[ 4588.212714]
[ 4588.212717] [<ffffffff811b3493>] tlb_flush_mmu.part.+0x33/0xc0
[ 4588.212717]
[ 4588.212719] [<ffffffff811b47b5>] tlb_finish_mmu+0x55/0x60
[ 4588.212719]
[ 4588.212721] [<ffffffff811b6d3a>] zap_page_range+0x13a/0x180
[ 4588.212721]
[ 4588.212723] [<ffffffff811bf0be>] ? do_mmap_pgoff+0x31e/0x3e0
[ 4588.212724]
[ 4588.212725] [<ffffffff811b2b5d>] SyS_madvise+0x3cd/0x9c0
[ 4588.212726]
[ 4588.212727] [<ffffffff816bd721>] ? __do_page_fault+0x171/0x450
[ 4588.212728]
[ 4588.212729] [<ffffffff816bdae6>] ? trace_do_page_fault+0x56/0x150
[ 4588.212730]
[ 4588.212733] [<ffffffff816c2789>] system_call_fastpath+0x16/0x1b
cpu17在刷新tlb，它需要发送ipi给其他的cpu，简单查看一下，
crash> dis -l ffffffff810fe46a
/usr/src/debug/kernel-3.10.-693.21..el7/linux-3.10.-693.21..el7.x86_64/kernel/smp.c:
0xffffffff810fe46a <smp_call_function_many+>: testb $0x1,0x20(%rcx) 110 行对应的代码是：
static void csd_lock_wait(struct call_single_data *csd)
{
while (csd->flags & CSD_FLAG_LOCK)
其实就是在执行 smp_call_function_many 调用的csd_lock_wait函数：
void smp_call_function_many(const struct cpumask *mask,
smp_call_func_t func, void *info, bool wait)
{
struct call_function_data *cfd;
int cpu, next_cpu, this_cpu = smp_processor_id(); /*
* Can deadlock when called with interrupts disabled.
* We allow cpu's that are not yet online though, as no one else can
* send smp call function interrupt to this cpu and as such deadlocks
* can't happen.
*/
WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
&& !oops_in_progress && !early_boot_irqs_disabled); /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
cpu = cpumask_first_and(mask, cpu_online_mask);
if (cpu == this_cpu)
cpu = cpumask_next_and(cpu, mask, cpu_online_mask); /* No online cpus? We're done. */
if (cpu >= nr_cpu_ids)
return; /* Do we have another CPU which isn't us? */
next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
if (next_cpu == this_cpu)
next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); /* Fastpath: do that cpu by itself. */
if (next_cpu >= nr_cpu_ids) {
smp_call_function_single(cpu, func, info, wait);
return;
} cfd = &__get_cpu_var(cfd_data); cpumask_and(cfd->cpumask, mask, cpu_online_mask);
cpumask_clear_cpu(this_cpu, cfd->cpumask);//将当前cpu排除在外 /* Some callers race with other cpus changing the passed mask */
if (unlikely(!cpumask_weight(cfd->cpumask)))
return; for_each_cpu(cpu, cfd->cpumask) {
struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu); csd_lock(csd);
csd->func = func;
csd->info = info;
llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
} /* Send a message to all CPUs in the map */
arch_send_call_function_ipi_mask(cfd->cpumask); if (wait) {
for_each_cpu(cpu, cfd->cpumask) {------------------------------按顺序等各个cpu修改csd的flag，不然我们就死等
struct call_single_data *csd; csd = per_cpu_ptr(cfd->csd, cpu);
csd_lock_wait(csd);-------------在执行这个
}
}
}
根据rcx的值，可以知道当前csd就是 0xffff880b52b9bfa0，我们知道csd是一个percpu变量，发起ipi的一方，通过构造一个csd挂到对方cpu的
call_single_queue percpu变量中，然后调用 arch_send_call_function_ipi_mask 来发送一个ipi，对方cpu在处理ipi的时候，则从自己的 call_single_queue 变量中，取出对应的ipi来完成，完成之后，设置对应的flag，然后等待的一方，循环检测这个flag是否达到预期，如果达到，则开始等待下一个，直到所有的cpumask中的cpu都反馈为止，执行ipi的回调函数的入口一般为：
/**
* generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
*
* Invoked by arch to handle an IPI for call function single.
* Must be called with interrupts disabled.
*/
void generic_smp_call_function_single_interrupt(void)
{
flush_smp_call_function_queue(true);
}
17号cpu既然在等待，那么哪些csd没有完成呢？我们知道当前等待的csd是：
crash> struct call_single_data ffff880b52b9bfa0
struct call_single_data {
{
llist = {
next = 0x0
},
__UNIQUE_ID_rh_kabi_hide1 = {
list = {
next = 0x0,
prev = 0x0
}
},
{<No data fields>}
},
func = 0xffffffff810706a0 <flush_tlb_func>,
info = 0xffff880aa7fdbcf8,
flags =
}
crash> struct flush_tlb_info 0xffff880aa7fdbcf8
struct flush_tlb_info {
flush_mm = 0xffff88168b3c5dc0,
flush_start = ,
flush_end =
}
根据cfd和csd的运算关系，由如下几行代码：
cfd = &__get_cpu_var(cfd_data);
。。。。。
struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
#define per_cpu_ptr(ptr, cpu) SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu)))
#define per_cpu_offset(x) (__per_cpu_offset[x])
可以确定17号等待的csd是6号cpu的。kmem -o的打印是显示的各个cpu的偏移。
crash> kmem -o
PER-CPU OFFSET VALUES:
CPU : ffff880b52a00000
CPU : ffff880b52a40000
CPU : ffff880b52a80000
CPU : ffff880b52ac0000
CPU : ffff880b52b00000
CPU : ffff880b52b40000
CPU : ffff880b52b80000
CPU : ffff880b52bc0000
CPU : ffff880b52c00000
CPU : ffff880b52c40000
CPU : ffff880b52c80000
CPU : ffff880b52cc0000
CPU : ffff881692200000
CPU : ffff881692240000
CPU : ffff881692280000
CPU : ffff8816922c0000
CPU : ffff881692300000
CPU : ffff881692340000
CPU : ffff881692380000
CPU : ffff8816923c0000
CPU : ffff881692400000
CPU : ffff881692440000
CPU : ffff881692480000
CPU : ffff8816924c0000
crash> px cfd_data:17
per_cpu(cfd_data, 17) = $43 = {
csd = 0x1bfa0,
cpumask = 0xffff880beeb51c00
}
crash> px 0xffff880b52b9bfa0-0x1bfa0
$44 = 0xffff880b52b80000-------------------6号cpu的偏移
crash> p cfd_data
PER-CPU DATA TYPE:
struct call_function_data cfd_data;
PER-CPU ADDRESSES:
[0]: ffff880b52a18780
[1]: ffff880b52a58780
[2]: ffff880b52a98780
[3]: ffff880b52ad8780
[4]: ffff880b52b18780
[5]: ffff880b52b58780
[6]: ffff880b52b98780
[7]: ffff880b52bd8780
[8]: ffff880b52c18780
[9]: ffff880b52c58780
[10]: ffff880b52c98780
[11]: ffff880b52cd8780
[12]: ffff881692218780
[13]: ffff881692258780
[14]: ffff881692298780
[15]: ffff8816922d8780
[16]: ffff881692318780
[17]: ffff881692358780
[18]: ffff881692398780
[19]: ffff8816923d8780
[20]: ffff881692418780
[21]: ffff881692458780
[22]: ffff881692498780
[23]: ffff8816924d8780
那6号cpu在干啥呢？
crash> set -c
PID:
COMMAND: "zte_uep1"
TASK: ffff880a207ccf10 [THREAD_INFO: ffff880a7766c000]
CPU:
STATE: TASK_RUNNING (ACTIVE)
crash> bt
PID: TASK: ffff880a207ccf10 CPU: COMMAND: "zte_uep1"
[exception RIP: native_queued_spin_lock_slowpath+]
RIP: ffffffff810fed1d RSP: ffff880a7766f798 RFLAGS:
RAX: RBX: RCX:
RDX: RSI: RDI: ffffffff81e991c0
RBP: ffff880a7766f798 R8: R9: 000000000000000c
R10: R11: R12: ffffffff81e991c0
R13: ffff88168d655368 R14: ffff880a7766f800 R15:
CS: SS:
# [ffff880a7766f7a0] queued_spin_lock_slowpath at ffffffff816abe64
# [ffff880a7766f7b0] _raw_spin_lock_irqsave at ffffffff816b92d7
# [ffff880a7766f7c8] lock_timer_base at ffffffff8109b4ab
# [ffff880a7766f7f8] mod_timer_pending at ffffffff8109c3c3
# [ffff880a7766f840] __nf_ct_refresh_acct at ffffffffc04be990 [nf_conntrack]
# [ffff880a7766f870] tcp_packet at ffffffffc04c7523 [nf_conntrack]
# [ffff880a7766f928] nf_conntrack_in at ffffffffc04c112a [nf_conntrack]
# [ffff880a7766f9d0] ipv4_conntrack_local at ffffffffc044366f [nf_conntrack_ipv4]
# [ffff880a7766f9e0] nf_iterate at ffffffff815cb818
# [ffff880a7766fa20] nf_hook_slow at ffffffff815cb908
# [ffff880a7766fa58] __ip_local_out_sk at ffffffff815d9a16
# [ffff880a7766faa8] ip_local_out_sk at ffffffff815d9a3b
# [ffff880a7766fac8] ip_queue_xmit at ffffffff815d9dc3
# [ffff880a7766fb00] tcp_transmit_skb at ffffffff815f40cc
# [ffff880a7766fb70] tcp_write_xmit at ffffffff815f484c
# [ffff880a7766fbd8] __tcp_push_pending_frames at ffffffff815f552e
# [ffff880a7766fbf0] tcp_push at ffffffff815e347c
# [ffff880a7766fc00] tcp_sendmsg at ffffffff815e6e40
# [ffff880a7766fcc8] inet_sendmsg at ffffffff816133a9
# [ffff880a7766fcf8] sock_sendmsg at ffffffff815753a6
# [ffff880a7766fe58] SYSC_sendto at ffffffff81575911
# [ffff880a7766ff70] sys_sendto at ffffffff8157639e
# [ffff880a7766ff80] system_call_fastpath at ffffffff816c2789
RIP: 00007fbe5777572b RSP: 00007fbe217d4158 RFLAGS:
RAX: 000000000000002c RBX: ffffffff816c2789 RCX:
RDX: RSI: 00007fbe217c4090 RDI: 00000000000000af
RBP: R8: R9:
R10: R11: R12: ffffffff8157639e
R13: ffff880a7766ff78 R14: 00007fbe217c4010 R15:
ORIG_RAX: 000000000000002c CS: SS: 002b
RFLAGS（64位）将EFLAGS（32位）扩展到64位，新扩展的高32位全部保留未用。
RFLAGS为0x93，换算成2进制，第9位IF就是0,
IF(bit 9) [Interrupt enable flag] 该标志用于控制处理器对可屏蔽中断请求(maskable interrupt requests)的响应。置1以响应可屏蔽中断，反之则禁止可屏蔽中断。就是关中断了，这个和堆栈是对得上的，堆栈明显在_raw_spin_lock_irqsave 等锁：
可以看出_spin_lock_irq的参数通过rdi传递(x86_64架构的传参规则，从左到右依次rdi、rsi...)，而rdi在后续的函数中没有再使用，所以最终上下文中的rdi即为参数的值：ffffffff81e991c0(bt中有RDI寄存器的值) ，为了进一步验证，我们来看下6号cpu积压的ipi：
crash> p call_single_queue:
per_cpu(call_single_queue, ) = $ = {
first = 0xffff880b52b9bd70
}
crash> list 0xffff880b52b9bd70
ffff880b52b9bd70
ffff880b52b9bfa0 crash> struct call_single_data ffff880b52b9bd70------------------------3号cpu发来的ipi请求，
struct call_single_data {
{
llist = {
next = 0xffff880b52b9bfa0
},
__UNIQUE_ID_rh_kabi_hide1 = {
list = {
next = 0xffff880b52b9bfa0,
prev = 0x0
}
},
{<No data fields>}
},
func = 0xffffffff810706a0 <flush_tlb_func>,
info = 0xffff8814f160fb58,
flags =
}
crash> struct call_single_data ffff880b52b9bfa0
struct call_single_data {
{
llist = {
next = 0x0
},
__UNIQUE_ID_rh_kabi_hide1 = {
list = {
next = 0x0,
prev = 0x0
}
},
{<No data fields>}
},
func = 0xffffffff810706a0 <flush_tlb_func>,
info = 0xffff880aa7fdbcf8,--------------------------6号cpu发送来的ipi请求
flags =
}
从积压的情况来看，有两个ipi没有处理，17号cpu发过来的ipi请求还排在后面，说明从时间上说，6号cpu关中断来获取锁的时候，17号cpu的ipi请求还没到。实际上6号cpu积压了一个3号cpu发来的ipi，以及17号cpu发来的ipi。
crash> bt
PID: TASK: ffff8809e7f2cf10 CPU: COMMAND: "zte_uep1"
[exception RIP: smp_call_function_many+]
RIP: ffffffff810fe46a RSP: ffff8814f160fb10 RFLAGS:
RAX: RBX: RCX: ffff880b52b9bd70--------------------在等6号cpu
RDX: RSI: RDI:
RBP: ffff8814f160fb48 R8: ffff88016e791000 R9: ffffffff8132a699
R10: ffff880b52adabc0 R11: ffffea002548e000 R12:
R13: ffffffff810706a0 R14: ffff8814f160fb58 R15: ffff880b52ad8780
CS: SS:
# [ffff8814f160fb50] native_flush_tlb_others at ffffffff81070868
# [ffff8814f160fba0] flush_tlb_page at ffffffff81070a64
# [ffff8814f160fbc0] ptep_clear_flush at ffffffff811c8984
# [ffff8814f160fbf8] try_to_unmap_one at ffffffff811c2bb2
# [ffff8814f160fc60] try_to_unmap_anon at ffffffff811c460d
# [ffff8814f160fca8] try_to_unmap at ffffffff811c46cd
# [ffff8814f160fcc0] migrate_pages at ffffffff811ed44f
# [ffff8814f160fd68] migrate_misplaced_page at ffffffff811ee11c
# [ffff8814f160fdb0] do_numa_page at ffffffff811b6f68
# [ffff8814f160fe00] handle_mm_fault at ffffffff811b8377
# [ffff8814f160fe98] __do_page_fault at ffffffff816bd704
# [ffff8814f160fef8] trace_do_page_fault at ffffffff816bdae6
# [ffff8814f160ff38] do_async_page_fault at ffffffff816bd17a
# [ffff8814f160ff50] async_page_fault at ffffffff816b9c38
RIP: 00007fbe56dc98d3 RSP: 00007fbb3eceb790 RFLAGS:
RAX: 00000000e2c27930 RBX: 0000000000001f42 RCX: 00000000e2c30000
RDX: 0000000000000e67 RSI: 00000000e2c27930 RDI: 00007fbe5701b790
RBP: 00007fbb3eceb7c0 R8: 00007fbe50021b18 R9: 0000000000001f40
R10: 0000000000000e67 R11: R12:
R13: 00007fbbb4040938 R14: 000000000000fa00 R15: 00007fbbb4045800
ORIG_RAX: ffffffffffffffff CS: SS: 002b
3号cpu，17号cpu都在等6号cpu，
crash> p call_single_queue:
per_cpu(call_single_queue, ) = $ = {
first = 0x0
}
crash> p call_single_queue:
per_cpu(call_single_queue, ) = $ = {
first = 0x0
}
3号核17号都没有积压的ipi处理，且都没有关中断，说明他俩是受害者。3号有没有阻塞别人呢，查看3号的堆栈，它拿了一把 ffffea002676cc30 的自旋锁，阻塞了如下的进程：
crash> search -t ffffea002676cc30
PID: TASK: ffff880afa3b5ee0 CPU: COMMAND: "zte_uep1"
ffff8809acf8fd48: ffffea002676cc30 PID: TASK: ffff8809a6b61fa0 CPU: COMMAND: "zte_uep1"
ffff88095b2f7d48: ffffea002676cc30 PID: TASK: ffff8809a4ad3f40 CPU: COMMAND: "zte_uep1"
ffff8809a6bf3d48: ffffea002676cc30 PID: TASK: ffff8809a4ad2f70 CPU: COMMAND: "zte_uep1"
ffff880985b53d48: ffffea002676cc30 PID: TASK: ffff8815dd2c8000 CPU: COMMAND: "zte_uep1"
ffff88009865bd48: ffffea002676cc30 PID: TASK: ffff8809e7f2cf10 CPU: COMMAND: "zte_uep1"-------------------3号拿了 fffea002676cc30的锁
ffff8814f160fc20: ffffea002676cc30
ffff8814f160fda0: ffffea002676cc30 PID: TASK: ffff8815cbfcaf70 CPU: COMMAND: "zte_uep1"
ffff8815a9f0bd48: ffffea002676cc30 PID: TASK: ffff880a6e3c8fd0 CPU: COMMAND: "zte_uep1"
ffff880a11ef3d48: ffffea002676cc30 PID: TASK: ffff8809e0376eb0 CPU: COMMAND: "zte_uep1"
ffff8809ac6fbd48: ffffea002676cc30 PID: TASK: ffff8809cbe02f70 CPU: COMMAND: "zte_uep1"
ffff8809a4a37d48: ffffea002676cc30
10号，4号，1号，13号，16号，18号，22号，2号，9号全部被cpu 3号阻塞，3号，17号被6号阻塞，
再分析其他cpu的等待关系：
如下，说明7在等0，而0在idle，说明7等0是一个瞬间状态，因为smp_call_function_many正要处理
crash> bt -c 7
PID: 3714 TASK: ffff881689e24f10 CPU: 7 COMMAND: "modprobe"
[exception RIP: smp_call_function_many+522]
RIP: ffffffff810fe46a RSP: ffff880675e1fd70 RFLAGS: 00000202
RAX: 0000000000000000 RBX: 0000000000000018 RCX: ffff880b52a1be10----------------等待的csd
RDX: 0000000000000000 RSI: 0000000000000018 RDI: 0000000000000000
RBP: ffff880675e1fda8 R8: ffff88016e792000 R9: ffffffff8132a699
R10: ffff880b52bdabc0 R11: ffffea002643f800 R12: 0000000000018740
R13: ffffffff8106a8c0 R14: 0000000000000000 R15: ffff880b52bd8780
CS: 0010 SS: 0018
#0 [ffff880675e1fdb0] on_each_cpu at ffffffff810fe52d
#1 [ffff880675e1fdd8] change_page_attr_set_clr at ffffffff8106c566
#2 [ffff880675e1fe88] set_memory_x at ffffffff8106c7d3
#3 [ffff880675e1fea8] unset_module_core_ro_nx at ffffffff8110096b
#4 [ffff880675e1fec0] free_module at ffffffff81102e7e
#5 [ffff880675e1fef8] sys_delete_module at ffffffff811030c7
#6 [ffff880675e1ff80] system_call_fastpath at ffffffff816c2789
RIP: 00007f3f44afa857 RSP: 00007ffc32e48b38 RFLAGS: 00000246
RAX: 00000000000000b0 RBX: ffffffff816c2789 RCX: ffffffffffffffff
RDX: 0000000000000000 RSI: 0000000000000800 RDI: 00000000021d99d8
RBP: 0000000000000000 R8: 00007f3f44dbf060 R9: 00007f3f44b6bae0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00000000021d7380 R14: 00000000021d9970 R15: 000000000ba846a1
ORIG_RAX: 00000000000000b0 CS: 0033 SS: 002b crash> p call_single_queue:0
per_cpu(call_single_queue, 0) = $79 = {
first = 0xffff880b52a1be10-------------0号cpu还未处理的csd
}
crash> list 0xffff880b52a1be10
ffff880b52a1be10
7号在等0号，0号是idle态进入irq处理，说明是瞬间情况。cpu 5，cpu6，cpu8，cpu11，cpu12，cpu14 ，cpu23都在等待 ffffffff81e991c0 这把锁。
19在等8，
crash> p call_single_queue:
per_cpu(call_single_queue, ) = $ = {
first = 0xffff8815ac3abc00
}
crash> list 0xffff8815ac3abc00
ffff8815ac3abc00
crash> call_single_data 0xffff8815ac3abc00
struct call_single_data {
{
llist = {
next = 0x0
},
__UNIQUE_ID_rh_kabi_hide3 = {
list = {
next = 0x0,
prev = 0x0
}
},
{<No data fields>}
},
func = 0xffffffff810706a0 <flush_tlb_func>,
info = 0xffff8815ac3abcd8,
flags =
}
cpu20在等11：
crash> bt -c
PID: TASK: ffff8809f1e20000 CPU: COMMAND: "java"
[exception RIP: generic_exec_single+]
RIP: ffffffff810fddca RSP: ffff8809b4e9fc00 RFLAGS:
RAX: RBX: ffff8809b4e9fc00 RCX:
RDX: 0000000000ffffff RSI: RDI:
RBP: ffff8809b4e9fc50 R8: ffffffff816de2e0 R9:
R10: R11: R12: 000000000000000b-------------等待的cpu号
R13: R14: ffff8809b4e9fcd8 R15: 000000000000000b
CS: SS:
# [ffff8809b4e9fc58] smp_call_function_single at ffffffff810fdedf
# [ffff8809b4e9fc88] smp_call_function_many at ffffffff810fe48b
# [ffff8809b4e9fcd0] native_flush_tlb_others at ffffffff81070868
# [ffff8809b4e9fd20] flush_tlb_mm_range at ffffffff81070938
# [ffff8809b4e9fd50] change_protection_range at ffffffff811c0228
# [ffff8809b4e9fe50] change_protection at ffffffff811c0385
# [ffff8809b4e9fe88] change_prot_numa at ffffffff811d8e8b
# [ffff8809b4e9fe98] task_numa_work at ffffffff810cd1a2
# [ffff8809b4e9fef0] task_work_run at ffffffff810b0abb
# [ffff8809b4e9ff30] do_notify_resume at ffffffff8102ab62
# [ffff8809b4e9ff50] int_signal at ffffffff816c2a3d
RIP: 00007f9c761c5a82 RSP: 00007f9c4fae3450 RFLAGS:
RAX: ffffffffffffff92 RBX: 0000000003810f00 RCX: ffffffffffffffff
RDX: RSI: RDI: 0000000003810f54
RBP: 00007f9c4fae3500 R8: 0000000003810f28 R9: 00000000ffffffff
R10: 00007f9c4fae34c0 R11: R12:
R13: 00007f9c4fae34c0 R14: ffffffffffffff92 R15: 00000000293f1200
ORIG_RAX: 00000000000000ca CS: SS: 002b
crash> dis -l generic_exec_single+
/usr/src/debug/kernel-3.10.-693.21..el7/linux-3.10.-693.21..el7.x86_64/kernel/smp.c:
0xffffffff810fddca <generic_exec_single+>: testb $0x1,0x20(%rbx)
crash> p call_single_queue:
per_cpu(call_single_queue, ) = $ = {
first = 0xffff8809b4e9fc00
}
同理可以分析，21cpu在等12cpu，
15号cpu啥都不等：
crash> bt -c 15
PID: 0 TASK: ffff880beeacbf40 CPU: 15 COMMAND: "swapper/15"
[exception RIP: lock_timer_base+26]
RIP: ffffffff8109b49a RSP: ffff8816922c3a10 RFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88098fee0100 RSI: ffff8816922c3a40 RDI: ffff8815d6b661e8
RBP: ffff8816922c3a30 R8: 0000000000000001 R9: 000000000000000c
R10: 0000000000000001 R11: 0000000000000003 R12: 0000000000000000
R13: ffff8815d6b661e8 R14: ffff8816922c3a40 R15: 0000000000000003
CS: 0010 SS: 0018
综合来看，需要分析那个等timer的锁，
那cpu 5，cpu6，cpu8，cpu11，cpu12，cpu14 ，cpu23号等待的锁 ffffffff81e991c0 到底被谁拿了呢？
crash> bt -c 5
PID: 28932 TASK: ffff8809ce2d1fa0 CPU: 5 COMMAND: "java"
[exception RIP: native_queued_spin_lock_slowpath+29]
RIP: ffffffff810fed1d RSP: ffff8800b975b758 RFLAGS: 00000093
RAX: 0000000000000001 RBX: 0000000000000286 RCX: 0000000000000001
RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffffffff81e991c0------------和cpu6等的锁是同一把
RBP: ffff8800b975b758 R8: 0000000000000001 R9: 000000000000000c
R10: 0000000000000000 R11: 0000000000000003 R12: ffffffff81e991c0
R13: ffff880b30e85ea8 R14: ffff8800b975b7c0 R15: 0000000000000003
CS: 0010 SS: 0018
#0 [ffff8800b975b760] queued_spin_lock_slowpath at ffffffff816abe64
#1 [ffff8800b975b770] _raw_spin_lock_irqsave at ffffffff816b92d7
#2 [ffff8800b975b788] lock_timer_base at ffffffff8109b4ab
#3 [ffff8800b975b7b8] mod_timer_pending at ffffffff8109c3c3
crash> kmem ffffffff81e991c0
ffffffff81e991c0 (B) boot_tvec_bases PAGE PHYSICAL MAPPING INDEX CNT FLAGS
ffffea000007a640 1e99000 1fffff00000400 reserved
crash> p boot_tvec_bases
boot_tvec_bases = $ = {
lock = {
{
rlock = {
raw_lock = {
val = {
counter = 1----------------------被人拿了
}
}
}
}
},
running_timer = 0x0,
timer_jiffies = ,
next_timer = ,
active_timers = ,
没有开启debug，没法直接获取到owner，各个active进程的堆栈也都搜过，没有搜到这个锁的占用。
这个其实就是tvec_bases 的第0号cpu的锁，为啥这么多cpu等0号cpu变量的锁呢？
通过堆栈可以知道，这些 等待锁的堆栈都是在做一件事情，那就是
lock_timer_base，但是这个锁却没有看到被谁占用，至今未能查出。如果有兄弟见过类似问题，希望能告知一二。
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