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? thanks, greg k-h
