blktrace: fix unlocked registration of tracepoints
We need to ensure that tracepoints are registered and unregistered
with the users of them. The existing atomic count isn't enough for
that. Add a lock around the tracepoints, so we serialize access
to them.
This fixes cases where we have multiple users setting up and
tearing down tracepoints, like this:
CPU: 0 PID: 2995 Comm: syzkaller857118 Not tainted
4.14.0-rc5-next-
20171018+ #36
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:52
panic+0x1e4/0x41c kernel/panic.c:183
__warn+0x1c4/0x1e0 kernel/panic.c:546
report_bug+0x211/0x2d0 lib/bug.c:183
fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:177
do_trap_no_signal arch/x86/kernel/traps.c:211 [inline]
do_trap+0x260/0x390 arch/x86/kernel/traps.c:260
do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:297
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:310
invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
RIP: 0010:tracepoint_add_func kernel/tracepoint.c:210 [inline]
RIP: 0010:tracepoint_probe_register_prio+0x397/0x9a0 kernel/tracepoint.c:283
RSP: 0018:
ffff8801d1d1f6c0 EFLAGS:
00010293
RAX:
ffff8801d22e8540 RBX:
00000000ffffffef RCX:
ffffffff81710f07
RDX:
0000000000000000 RSI:
ffffffff85b679c0 RDI:
ffff8801d5f19818
RBP:
ffff8801d1d1f7c8 R08:
ffffffff81710c10 R09:
0000000000000004
R10:
ffff8801d1d1f6b0 R11:
0000000000000003 R12:
ffffffff817597f0
R13:
0000000000000000 R14:
00000000ffffffff R15:
ffff8801d1d1f7a0
tracepoint_probe_register+0x2a/0x40 kernel/tracepoint.c:304
register_trace_block_rq_insert include/trace/events/block.h:191 [inline]
blk_register_tracepoints+0x1e/0x2f0 kernel/trace/blktrace.c:1043
do_blk_trace_setup+0xa10/0xcf0 kernel/trace/blktrace.c:542
blk_trace_setup+0xbd/0x180 kernel/trace/blktrace.c:564
sg_ioctl+0xc71/0x2d90 drivers/scsi/sg.c:1089
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x444339
RSP: 002b:
00007ffe05bb5b18 EFLAGS:
00000206 ORIG_RAX:
0000000000000010
RAX:
ffffffffffffffda RBX:
00000000006d66c0 RCX:
0000000000444339
RDX:
000000002084cf90 RSI:
00000000c0481273 RDI:
0000000000000009
RBP:
0000000000000082 R08:
0000000000000000 R09:
0000000000000000
R10:
0000000000000000 R11:
0000000000000206 R12:
ffffffffffffffff
R13:
00000000c0481273 R14:
0000000000000000 R15:
0000000000000000
since we can now run these in parallel. Ensure that the exported helpers
for doing this are grabbing the queue trace mutex.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>