* [PATCH] tracing: Move postpone selftests to core from early_initcall
@ 2017-05-17 15:14 Steven Rostedt
2017-05-17 16:00 ` Paul E. McKenney
0 siblings, 1 reply; 2+ messages in thread
From: Steven Rostedt @ 2017-05-17 15:14 UTC (permalink / raw)
To: LKML; +Cc: Paul E. McKenney
I hit the following lockdep splat when booting with ftrace selftests
enabled, as well as CONFIG_PREEMPT and LOCKDEP.
Testing dynamic ftrace ops #1:
(1 0 1 0 0)
(1 1 2 0 0)
(2 1 3 0 169)
(2 2 4 0 50066)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 13 at kernel/rcu/srcutree.c:202 check_init_srcu_struct+0x60/0x70
Modules linked in:
CPU: 0 PID: 13 Comm: rcu_tasks_kthre Not tainted 4.12.0-rc1-test+ #587
Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
task: ffff880119628040 task.stack: ffffc900006a4000
RIP: 0010:check_init_srcu_struct+0x60/0x70
RSP: 0000:ffffc900006a7d98 EFLAGS: 00010246
RAX: 0000000000000246 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff880119628040 RSI: 00000000ffffffff RDI: ffffffff81e5fb40
RBP: ffffc900006a7e20 R08: 00000023b403c000 R09: 0000000000000001
R10: ffffc900006a7e40 R11: 0000000000000000 R12: ffffffff81e5fb40
R13: 0000000000000286 R14: ffff880119628040 R15: ffffc900006a7e98
FS: 0000000000000000(0000) GS:ffff88011ea00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff88011edff000 CR3: 0000000001e0f000 CR4: 00000000001406f0
Call Trace:
? __synchronize_srcu+0x6e/0x140
? lock_acquire+0xdc/0x1d0
? ktime_get_mono_fast_ns+0x5d/0xb0
synchronize_srcu+0x6f/0x110
? synchronize_srcu+0x6f/0x110
rcu_tasks_kthread+0x20a/0x540
kthread+0x114/0x150
? __rcu_read_unlock+0x70/0x70
? kthread_create_on_node+0x40/0x40
ret_from_fork+0x2e/0x40
Code: f6 83 70 06 00 00 03 49 89 c5 74 0d be 01 00 00 00 48 89 df e8 42 fa ff ff 4c 89 ee 4c 89 e7 e8 b7 42 75 00 5b 41 5c 41 5d 5d c3 <0f> ff eb aa 66 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00
---[ end trace 5c3f4206ce50f6ac ]---
What happens is that the selftests include a creating of a dynamically
allocated ftrace_ops, which requires the use of synchronize_rcu_tasks()
which uses srcu, and triggers the above warning.
It appears that synchronize_rcu_tasks() is not set up at early_initcall(),
but it is at core_initcall(). By moving the tests down to that location
works out properly.
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3f2aed4..fcc9a2d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1558,7 +1558,7 @@ static __init int init_trace_selftests(void)
return 0;
}
-early_initcall(init_trace_selftests);
+core_initcall(init_trace_selftests);
#else
static inline int run_tracer_selftest(struct tracer *type)
{
--
2.9.3
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] tracing: Move postpone selftests to core from early_initcall
2017-05-17 15:14 [PATCH] tracing: Move postpone selftests to core from early_initcall Steven Rostedt
@ 2017-05-17 16:00 ` Paul E. McKenney
0 siblings, 0 replies; 2+ messages in thread
From: Paul E. McKenney @ 2017-05-17 16:00 UTC (permalink / raw)
To: Steven Rostedt; +Cc: LKML
On Wed, May 17, 2017 at 11:14:35AM -0400, Steven Rostedt wrote:
>
> I hit the following lockdep splat when booting with ftrace selftests
> enabled, as well as CONFIG_PREEMPT and LOCKDEP.
>
> Testing dynamic ftrace ops #1:
> (1 0 1 0 0)
> (1 1 2 0 0)
> (2 1 3 0 169)
> (2 2 4 0 50066)
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 13 at kernel/rcu/srcutree.c:202 check_init_srcu_struct+0x60/0x70
> Modules linked in:
> CPU: 0 PID: 13 Comm: rcu_tasks_kthre Not tainted 4.12.0-rc1-test+ #587
> Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
> task: ffff880119628040 task.stack: ffffc900006a4000
> RIP: 0010:check_init_srcu_struct+0x60/0x70
> RSP: 0000:ffffc900006a7d98 EFLAGS: 00010246
> RAX: 0000000000000246 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff880119628040 RSI: 00000000ffffffff RDI: ffffffff81e5fb40
> RBP: ffffc900006a7e20 R08: 00000023b403c000 R09: 0000000000000001
> R10: ffffc900006a7e40 R11: 0000000000000000 R12: ffffffff81e5fb40
> R13: 0000000000000286 R14: ffff880119628040 R15: ffffc900006a7e98
> FS: 0000000000000000(0000) GS:ffff88011ea00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffff88011edff000 CR3: 0000000001e0f000 CR4: 00000000001406f0
> Call Trace:
> ? __synchronize_srcu+0x6e/0x140
> ? lock_acquire+0xdc/0x1d0
> ? ktime_get_mono_fast_ns+0x5d/0xb0
> synchronize_srcu+0x6f/0x110
> ? synchronize_srcu+0x6f/0x110
> rcu_tasks_kthread+0x20a/0x540
> kthread+0x114/0x150
> ? __rcu_read_unlock+0x70/0x70
> ? kthread_create_on_node+0x40/0x40
> ret_from_fork+0x2e/0x40
> Code: f6 83 70 06 00 00 03 49 89 c5 74 0d be 01 00 00 00 48 89 df e8 42 fa ff ff 4c 89 ee 4c 89 e7 e8 b7 42 75 00 5b 41 5c 41 5d 5d c3 <0f> ff eb aa 66 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00
> ---[ end trace 5c3f4206ce50f6ac ]---
>
> What happens is that the selftests include a creating of a dynamically
> allocated ftrace_ops, which requires the use of synchronize_rcu_tasks()
> which uses srcu, and triggers the above warning.
>
> It appears that synchronize_rcu_tasks() is not set up at early_initcall(),
> but it is at core_initcall(). By moving the tests down to that location
> works out properly.
>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
But it looks like I need to raise the priority of making SRCU
safe throughout boot, including the "mid-boot dead zone"...
Thanx, Paul
> ---
> kernel/trace/trace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 3f2aed4..fcc9a2d 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1558,7 +1558,7 @@ static __init int init_trace_selftests(void)
>
> return 0;
> }
> -early_initcall(init_trace_selftests);
> +core_initcall(init_trace_selftests);
> #else
> static inline int run_tracer_selftest(struct tracer *type)
> {
> --
> 2.9.3
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2017-05-17 16:00 ` Paul E. McKenney
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