Hi,
-----Original Message----- From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: Thursday, July 18, 2019 12:03 PM To: iwamatsu nobuhiro(岩松 信洋 ○ＳＷＣ□ＯＳＴ) nobuhiro1.iwamatsu@toshiba.co.jp Cc: devel@etsukata.com; rostedt@goodmis.org; stable@vger.kernel.org Subject: Re: [PATCH for 4.4, 4.9] tracing/snapshot: Resize spare buffer if size changed
On Thu, Jul 18, 2019 at 11:55:47AM +0900, Nobuhiro Iwamatsu wrote:
From: Eiichi Tsukata devel@etsukata.com
Current snapshot implementation swaps two ring_buffers even though their sizes are different from each other, that can cause an inconsistency between the contents of buffer_size_kb file and the
current buffer size.
For example:
# cat buffer_size_kb 7 (expanded: 1408) # echo 1 > events/enable # grep bytes per_cpu/cpu0/stats bytes: 1441020 # echo 1 > snapshot // current:1408, spare:1408 # echo 123 > buffer_size_kb // current:123, spare:1408 # echo 1 > snapshot // current:1408, spare:123 # grep bytes per_cpu/cpu0/stats bytes: 1443700 # cat buffer_size_kb 123 // != current:1408
And also, a similar per-cpu case hits the following WARNING:
Reproducer:
# echo 1 > per_cpu/cpu0/snapshot # echo 123 > buffer_size_kb # echo 1 > per_cpu/cpu0/snapshot
WARNING:
WARNING: CPU: 0 PID: 1946 at kernel/trace/trace.c:1607
update_max_tr_single.part.0+0x2b8/0x380
Modules linked in: CPU: 0 PID: 1946 Comm: bash Not tainted 5.2.0-rc6 #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.12.0-2.fc30 04/01/2014
RIP: 0010:update_max_tr_single.part.0+0x2b8/0x380 Code: ff e8 dc da f9 ff 0f 0b e9 88 fe ff ff e8 d0 da f9 ff 44 89
ee bf f5 ff ff ff e8 33 dc f9 ff 41 83 fd f5 74 96 e8 b8 da f9 ff <0f> 0b eb 8d e8 af da f9 ff 0f 0b e9 bf fd ff ff e8 a3 da f9 ff 48
RSP: 0018:ffff888063e4fca0 EFLAGS: 00010093 RAX: ffff888066214380 RBX: ffffffff99850fe0 RCX: ffffffff964298a8 RDX: 0000000000000000 RSI: 00000000fffffff5 RDI: 0000000000000005 RBP: 1ffff1100c7c9f96 R08: ffff888066214380 R09: ffffed100c7c9f9b R10: ffffed100c7c9f9a R11: 0000000000000003 R12: 0000000000000000 R13: 00000000ffffffea R14: ffff888066214380 R15: ffffffff99851060 FS: 00007f9f8173c700(0000) GS:ffff88806d000000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000714dc0 CR3: 0000000066fa6000 CR4: 00000000000006f0 Call Trace: ? trace_array_printk_buf+0x140/0x140 ? __mutex_lock_slowpath+0x10/0x10 tracing_snapshot_write+0x4c8/0x7f0 ? trace_printk_init_buffers+0x60/0x60 ? selinux_file_permission+0x3b/0x540 ? tracer_preempt_off+0x38/0x506 ? trace_printk_init_buffers+0x60/0x60 __vfs_write+0x81/0x100 vfs_write+0x1e1/0x560 ksys_write+0x126/0x250 ? __ia32_sys_read+0xb0/0xb0 ? do_syscall_64+0x1f/0x390 do_syscall_64+0xc1/0x390 entry_SYSCALL_64_after_hwframe+0x49/0xbe
This patch adds resize_buffer_duplicate_size() to check if there is
a
difference between current/spare buffer sizes and resize a spare buffer if necessary.
Link: http://lkml.kernel.org/r/20190625012910.13109-1-devel@etsukata.com
Cc: stable@vger.kernel.org Fixes: ad909e21bbe69 ("tracing: Add internal tracing_snapshot() functions") Signed-off-by: Eiichi Tsukata devel@etsukata.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Nobuhiro Iwamatsu nobuhiro1.iwamatsu@toshiba.co.jp
kernel/trace/trace.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
What is the git commit id of this patch in Linus's tree?
Oh, sorry. I forgot it. I will resend updated patch.
Nobuhiro