Hi, > -----Original Message----- > From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx] > Sent: Thursday, July 18, 2019 12:03 PM > To: iwamatsu nobuhiro(岩松 信洋 ○ＳＷＣ□ＯＳＴ) > <nobuhiro1.iwamatsu@xxxxxxxxxxxxx> > Cc: devel@xxxxxxxxxxxx; rostedt@xxxxxxxxxxx; stable@xxxxxxxxxxxxxxx > 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@xxxxxxxxxxxx> > > > > 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@xxxxxxxxxxxx > > > > Cc: stable@xxxxxxxxxxxxxxx > > Fixes: ad909e21bbe69 ("tracing: Add internal tracing_snapshot() > > functions") > > Signed-off-by: Eiichi Tsukata <devel@xxxxxxxxxxxx> > > Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> > > Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@xxxxxxxxxxxxx> > > --- > > 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
