* [lttng-dev] epoll_wait reboot kernel?
2014-02-24 9:36 ` zhenyu.ren
2014-02-24 15:08 ` Mathieu Desnoyers
@ 2014-02-25 6:01 ` zhenyu.ren
1 sibling, 0 replies; 4+ messages in thread
From: zhenyu.ren @ 2014-02-25 6:01 UTC (permalink / raw)
>Which gcc version do you use ?
$gcc --version
gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-46)
I disassembed lib_ring_buffer_write() and focused on how it calles lib_ring_buffer_do_copy(indeed inline_memcpy)
void lib_ring_buffer_write(const struct lib_ring_buffer_config *config,
struct lib_ring_buffer_ctx *ctx,
const void *src, size_t len)
{
struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
struct channel_backend *chanb = &ctx->chan->backend;
size_t sbidx, index;
size_t offset = ctx->buf_offset;
ssize_t pagecpy;
struct lib_ring_buffer_backend_pages *rpages;
unsigned long sb_bindex, id;
if (unlikely(!len))
return;
offset &= chanb->buf_size - 1;
sbidx = offset >> chanb->subbuf_size_order;
index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
id = bufb->buf_wsb[sbidx].id;
sb_bindex = subbuffer_id_get_index(config, id);
rpages = bufb->array[sb_bindex];
CHAN_WARN_ON(ctx->chan,
config->mode == RING_BUFFER_OVERWRITE
&& subbuffer_id_is_noref(config, id));
if (likely(pagecpy == len))
lib_ring_buffer_do_copy(config,
rpages->p[index].virt
+ (offset & ~PAGE_MASK),
src, len);
else
_lib_ring_buffer_write(bufb, offset, src, len, 0);
ctx->buf_offset += len;
}
00000000000003a0 <lib_ring_buffer_write>:
3a0: 55 push %rbp
3a1: 48 89 e5 mov %rsp,%rbp
3a4: 48 83 ec 40 sub $0x40,%rsp
3a8: 48 89 5d d8 mov %rbx,0xffffffffffffffd8(%rbp)
3ac: 4c 89 65 e0 mov %r12,0xffffffffffffffe0(%rbp)
3b0: 4c 89 6d e8 mov %r13,0xffffffffffffffe8(%rbp)
3b4: 4c 89 75 f0 mov %r14,0xfffffffffffffff0(%rbp)
3b8: 4c 89 7d f8 mov %r15,0xfffffffffffffff8(%rbp)
3bc: e8 00 00 00 00 callq 3c1 <lib_ring_buffer_write+0x21>
3c1: 49 89 f5 mov %rsi,%r13 rsi/r13-> ctx
3c4: 48 85 c9 test %rcx,%rcx rcx-> len
3c7: 48 89 55 c8 mov %rdx,0xffffffffffffffc8(%rbp) rdx/c8-> src
3cb: 49 89 cc mov %rcx,%r12 rcx/r12-> len
3ce: 48 8b 76 20 mov 0x20(%rsi),%rsi rsi-> ctx->buf
3d2: 4d 8b 45 00 mov 0x0(%r13),%r8 r8-> ctx->chan
3d6: 49 8b 55 30 mov 0x30(%r13),%rdx rdx-> offset = ctx->buf_offset
3da: 0f 84 a5 00 00 00 je 485 <lib_ring_buffer_write+0xe5> if(!len) return
3e0: 49 8b 58 10 mov 0x10(%r8),%rbx rbx-> ctx->chan->backend
3e4: 49 8d 40 10 lea 0x10(%r8),%rax rax-> *chanb = &ctx->chan->backend
3e8: 4c 8d 76 28 lea 0x28(%rsi),%r14 r14-> *bufb = &ctx->buf->backend
3ec: 48 83 eb 01 sub $0x1,%rbx rbx-> chanb->buf_size - 1
3f0: 48 21 d3 and %rdx,%rbx rbx-> offset &= chanb->buf_size -1
3f3: 48 8b 50 08 mov 0x8(%rax),%rdx rdx-> chanb->subbuf_size
3f7: 48 89 55 d0 mov %rdx,0xffffffffffffffd0(%rbp) d0-> chanb->subbuf_size
3fb: 8b 48 10 mov 0x10(%rax),%ecx ecx-> chanb->subbuf_size_order
3fe: 48 89 da mov %rbx,%rdx rdx-> offset
401: 48 8b 46 28 mov 0x28(%rsi),%rax rax-> bufb = &ctx->buf->backen
405: 48 d3 ea shr %cl,%rdx rdx-> sbidx = offset >> chanb->subbuf_size_orde
408: 48 8b 0c d0 mov (%rax,%rdx,8),%rcx rcx-> id = bufb->buf_wsb[sbidx].id
40c: 8b 47 08 mov 0x8(%rdi),%eax eax-> config->mode
40f: 85 c0 test %eax,%eax CHAN_WARN_ON(... (config->mode == RING_BUFFER_OVERWRITE)...)
411: 0f 85 89 00 00 00 jne 4a0 <lib_ring_buffer_write+0x100>
417: 49 8b 46 10 mov 0x10(%r14),%rax rax-> bufb->array
41b: 48 89 ca mov %rcx,%rdx rdx-> id
41e: 83 e2 ff and $0xffffffffffffffff,%edx
421: 4c 8b 3c d0 mov (%rax,%rdx,8),%r15 r15-> rpages = bufb->array[sb_binde
425: 48 b8 00 00 00 00 01 mov $0x100000000,%rax rax-> SB_ID_NOREF_MASK
42c: 00 00 00
42f: 48 85 c8 test %rcx,%rax id & SB_ID_NOREF_MASK
432: 0f 95 c0 setne %al
435: 0f b6 c0 movzbl %al,%eax
438: 48 85 c0 test %rax,%rax if(config->mode==RING_BUFFER_OVERWRITE && subbuffer_id_is_noref(config,id))
43b: 75 6f jne 4ac <lib_ring_buffer_write+0x10c>
43d: 48 89 d8 mov %rbx,%rax rax-> offset
440: 48 f7 d8 neg %rax rax-> -offset
443: 25 ff 0f 00 00 and $0xfff,%eax eax-> (-offset) & ~PAGE_MASK
448: 49 39 c4 cmp %rax,%r12 cmp(len,(-offset) & ~PAGE_MASK)
44b: 49 0f 46 c4 cmovbe %r12,%rax rax-> pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK)
44f: 4c 39 e0 cmp %r12,%rax if(pagecpy == len)
452: 75 72 jne 4c6 <lib_ring_buffer_write+0x126> jmp to call _lib_ring_buffer_write()
454: 48 8b 45 d0 mov 0xffffffffffffffd0(%rbp),%rax rax-> chanb->subbuf_size
458: 48 8b 75 c8 mov 0xffffffffffffffc8(%rbp),%rsi rsi-> src
45c: 48 83 e8 01 sub $0x1,%rax rax-> chanb->subbuf_size - 1
460: 48 21 d8 and %rbx,%rax rax-> offset & (chanb->subbuf_size - 1)
463: 81 e3 ff 0f 00 00 and $0xfff,%ebx ebx-> offset & ~PAGE_MASK
469: 48 c1 e8 0c shr $0xc,%rax rax-> index=(offset&(chanb->subbuf_size-1))>>PAGE_SHIFT
46d: 48 c1 e0 04 shl $0x4,%rax rax-> index
471: 4a 03 5c 38 20 add 0x20(%rax,%r15,1),%rbx rbx-> rpages->p[index].virt+ (offset & ~PAGE_MASK)
476: 48 89 da mov %rbx,%rdx rdx-> SHOULD BE inline_memcpy() the 3rd parameter:len
479: 48 89 df mov %rbx,%rdi rdi-> 1st parameter
47c: e8 00 00 00 00 callq 481 <lib_ring_buffer_write+0xe1> call inline_memcpy(dst,src,len)
481: 4d 01 65 30 add %r12,0x30(%r13) ctx->buf_offset += len(r12)
485: 48 8b 5d d8 mov 0xffffffffffffffd8(%rbp),%rbx
489: 4c 8b 65 e0 mov 0xffffffffffffffe0(%rbp),%r12
48d: 4c 8b 6d e8 mov 0xffffffffffffffe8(%rbp),%r13
491: 4c 8b 75 f0 mov 0xfffffffffffffff0(%rbp),%r14
495: 4c 8b 7d f8 mov 0xfffffffffffffff8(%rbp),%r15
499: c9 leaveq
49a: c3 retq
49b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
4a0: 49 8b 46 10 mov 0x10(%r14),%rax rax-> bufb->array
4a4: 4c 8b 3c c8 mov (%rax,%rcx,8),%r15 r15-> rpages = bufb->array[sb_bindex]
4a8: 31 c0 xor %eax,%eax eax-> 0
4aa: eb 8c jmp 438 <lib_ring_buffer_write+0x98> .......
4ac: f0 41 ff 00 lock incl (%r8) atomic_inc(&__chan->record_disabled
4b0: be 6e 00 00 00 mov $0x6e,%esi
4b5: 48 c7 c7 00 00 00 00 mov $0x0,%rdi
4bc: e8 00 00 00 00 callq 4c1 <lib_ring_buffer_write+0x121> WARN_ON(1);
4c1: e9 77 ff ff ff jmpq 43d <lib_ring_buffer_write+0x9d> ....... jmp to if (pagecpy == len)
4c6: 48 8b 55 c8 mov 0xffffffffffffffc8(%rbp),%rdx rdx-> src
4ca: 45 31 c0 xor %r8d,%r8d r8d-> 0
4cd: 4c 89 e1 mov %r12,%rcx r12/rcx-> len
4d0: 48 89 de mov %rbx,%rsi rbx/rsi-> offset
4d3: 4c 89 f7 mov %r14,%rdi r14/rdi-> bufb
4d6: e8 00 00 00 00 callq 4db <lib_ring_buffer_write+0x13b> _lib_ring_buffer_write(bufb, offset, src, len, 0);
4db: eb a4 jmp 481 <lib_ring_buffer_write+0xe1> ...... jmp to ctx->buf_offset += len and return
All difference with good case is also where I am insterested in:
bad case:
45c: 48 83 e8 01 sub $0x1,%rax rax-> chanb->subbuf_size - 1
460: 48 21 d8 and %rbx,%rax rax-> offset & (chanb->subbuf_size - 1)
463: 81 e3 ff 0f 00 00 and $0xfff,%ebx ebx-> offset & ~PAGE_MASK
469: 48 c1 e8 0c shr $0xc,%rax rax-> index=(offset&(chanb->subbuf_size-1))>>PAGE_SHIFT
46d: 48 c1 e0 04 shl $0x4,%rax rax-> index
471: 4a 03 5c 38 20 add 0x20(%rax,%r15,1),%rbx rbx-> rpages->p[index].virt+ (offset & ~PAGE_MASK)
476: 48 89 da mov %rbx,%rdx rdx-> SHOULD BE inline_memcpy() the 3rd parameter:len
479: 48 89 df mov %rbx,%rdi rdi-> 1st parameter
47c: e8 00 00 00 00 callq 481 <lib_ring_buffer_write+0xe1> call inline_memcpy(dst,src,len)
good case:
45c: 4c 89 e2 mov %r12,%rdx r12/rdx-> len
45f: 48 83 e8 01 sub $0x1,%rax rax-> chanb->subbuf_size - 1
463: 48 21 d8 and %rbx,%rax rax-> offset & (chanb->subbuf_size - 1)
466: 81 e3 ff 0f 00 00 and $0xfff,%ebx ebx-> offset & ~PAGE_MASK
46c: 48 c1 e8 0c shr $0xc,%rax rax-> index=(offset&(chanb->subbuf_size-1))>>PAGE_SHIFT
470: 48 c1 e0 04 shl $0x4,%rax rax-> index
474: 4a 03 5c 38 20 add 0x20(%rax,%r15,1),%rbx rbx-> rpages->p[index].virt+ (offset & ~PAGE_MASK)
479: 48 89 df mov %rbx,%rdi rdi-> dst , the 1st parameter of inline_memcpy(dst,src,len)
47c: e8 00 00 00 00 callq 481 <lib_ring_buffer_write+0xe1> call inline_memcpy(dst,src,len)
In good case, at line 45c, rdx ,which is the 3rd parameter of inline_memcpy(dst,src,len), comes from %r12 that is len.However,in bad case,at line 476, rdx comes from rbx that is the 1st parameter of inline_memcpy(dst,src,len). So you can image what will happen if len is too large.
I don't know why GCC produce the wrong code.Does anyone has any clue?
Thanks
zhenyu.ren
----- Original Message -----
> From: "zhenyu.ren" <zhenyu.ren@aliyun.com>
> To: "lttng-dev" <lttng-dev at lists.lttng.org>, "zhenyu.ren" <zhenyu.ren at aliyun.com>
> Sent: Monday, February 24, 2014 4:36:36 AM
> Subject: Re: [lttng-dev] epoll_wait reboot kernel?
>
> Oh,It seems not epoll related . I am using DBG/ERR() as debug way ,but this
> print-style method doesn't work as expected,so I mistake for epoll_wait.
> It seems gcc problem because if I changed lib_ring_buffer_do_copy as the
> following,all work well
>
> #define lib_ring_buffer_do_copy(config, dest, src, len) \
> do { \
> size_t __len1 = (len); \
> /*here , not __len=(len)*/
> mdelay(0x135);\
> if (__builtin_constant_p(len)) \
> memcpy(dest, src, __len1); \
> else \
> inline_memcpy(dest, src, __len1); \
> } while (0)
>
> I disasembled lib_ring_buffer_write() and "vimdiff bad good" shows :
> 49c: 48 89 da mov %rbx,%rdx
> | 49c:
> 4c 89 f2 mov %r14,%rdx
>
> here rdx is the 3rd parameter to inline_memcpy().
>
> Thanks
> zhenyu.ren
>
>
> >Hi,lttng-dev
> >
> > I am working on rhel6(2.6.32.220) and ust is working very well.But when I
> > use lttng-modules (after "lttng start"),the kernel reboots immediately
> > >without any message output to console.
> >
> > It took me some days finding out what results in reboot. I shortcut
> > __event_probe__##_name() before _tstruct but kernel still reboot(So what
> > left is >metadata_printf).If I comment out "mask |= POLLIN" in
> > lttng_metadata_ring_buffer_poll() ,kernel do not reboot. What I find out
> > is before reboot the >callchain of lttng-consumerd thread is
> > consumer_thread_metadata_poll()->lttng_poll_wait(wait for metadata
> > stream)->compat_epoll_wait().
> >
> > I want to use poll instead as epoll in lttng-tools ,I changed lttng-tools
> > configure file to not use epoll(undef HAVE_EPOLL),but "lttng enable-event
> > -a -k >"failed :(Do I miss anything?)
> >#lttng enable-event -a -k
> >DEBUG1 [17837/18080]: Wait for client response (in thread_manage_clients()
> >at main.c:3709)
> >DEBUG1 [17837/18080]: Receiving data from client ... (in
> >thread_manage_clients() at main.c:3754)
> >DEBUG1 [17837/18080]: Nothing recv() from client... continuing (in
> >thread_manage_clients() at main.c:3758)
> >DEBUG1 [17837/18080]: Clean command context structure (in
> >clean_command_ctx() at main.c:535)
> >DEBUG1 [17837/18080]: Accepting client command ... (in
> >thread_manage_clients() at main.c:3667)
> >DEBUG1 [17837/18080]: Wait for client response (in thread_manage_clients()
> >at main.c:3709)
> >DEBUG1 [17837/18080]: Receiving data from client ... (in
> >thread_manage_clients() at main.c:3754)
> >DEBUG1 [17837/18080]: Processing client command 7 (in process_client_msg()
> >at main.c:2579)
> >DEBUG1 [17837/18080]: Getting session k-test by name (in
> >process_client_msg() at main.c:2656)
> >DEBUG1 [17837/18080]: Creating kernel session (in create_kernel_session() at
> >main.c:2495)
> >DEBUG3 [17837/18080]: Created hashtable size 4 at 0x669410 of type 1 (in
> >lttng_ht_new() at hashtable.c:112)
> >DEBUG1 [17837/18080]: Kernel session created (fd: 21) (in
> >kernel_create_session() at kernel.c:109)
> >DEBUG3 [17837/18080]: Copying tracing session consumer output in kernel
> >session (in copy_session_consumer() at main.c:2393)
> >DEBUG3 [17837/18080]: Created hashtable size 4 at 0x66a750 of type 1 (in
> >lttng_ht_new() at hashtable.c:112)
> >DEBUG3 [17837/18080]: Copy session consumer subdir /kernel (in
> >copy_session_consumer() at main.c:2428)
> >DEBUG3 [17837/18080]: mkdir() recursive
> >/root/lttng-traces/k-test-20140222-131335 with mode 504 for uid 0 and gid 0
> >(in run_as_mkdir_recursive() at >runas.c:310)
> >DEBUG1 [17837/18080]: Using run_as_clone (in run_as() at runas.c:293)
> >lttng-sessiond: ht-cleanup.c:92: thread_ht_cleanup: Assertion `pollfd ==
> >ht_cleanup_pipe[0]' failed.
> >
> > It seems lttng-tools in ubuntu 12.04 is using poll,isnt it?
> >
> > Does anyone have any suggestions to me ?
>
> >PS:.lttng(ust/module/tool) version is 2.3.0 and urcu version is 0.8
>
>
> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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