From: Jason Gunthorpe <jgg@ziepe.ca>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Leonid Ravich <leonid.ravich@toganetworks.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Yigal Korman <yigal.korman@toganetworks.com>,
"linux-trace-kernel@vger.kernel.org"
<linux-trace-kernel@vger.kernel.org>,
Leon Ravich <lravich@gmail.com>
Subject: Re: BUG: ib_mad ftrace event unsupported migration
Date: Wed, 2 Nov 2022 11:24:20 -0300 [thread overview]
Message-ID: <Y2J9lAqBvjjPUmJf@ziepe.ca> (raw)
In-Reply-To: <20221102101719.6cbcca6b@rorschach.local.home>
On Wed, Nov 02, 2022 at 10:17:19AM -0400, Steven Rostedt wrote:
> On Wed, 2 Nov 2022 11:04:44 -0300
> Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> > So this tracepoint is just wrong, you can't call a sleepable function
> > from a tracepoint like that?
> >
> > Presumably lockdep would/should warn about this?
>
> Why didn't it trigger a "scheduling while atomic" bug? That should
> happen if you call a sleeping function while preemption is disabled. Or
> does this function explicitly enable preemption? Which nothing checks
> if you enable preemption while recording to the ring buffer. I guess we
> could add that check, but this is not something that commonly happens
> enough to bother.
No, it doesn't muck with preemption, it will have some sleeping lock,
eg mlx5_ib_query_pkey() does a memory allocation as the first thing
It seems like a bug that calling kmalloc(GFP_KERNEL)/might_sleep()
from within a tracepoint doesn't trigger a warning?
Jason
next prev parent reply other threads:[~2022-11-02 14:24 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 10:49 BUG: ib_mad ftrace event unsupported migration Leonid Ravich
2022-11-02 11:44 ` Steven Rostedt
2022-11-02 13:02 ` Jason Gunthorpe
2022-11-02 14:02 ` Leonid Ravich
2022-11-02 14:04 ` Jason Gunthorpe
2022-11-02 14:17 ` Steven Rostedt
2022-11-02 14:24 ` Jason Gunthorpe [this message]
2022-11-02 15:59 ` Steven Rostedt
2022-11-02 16:01 ` Jason Gunthorpe
2022-11-02 20:01 ` Leonid Ravich
2022-11-02 22:19 ` Steven Rostedt
2022-11-03 12:22 ` Leonid Ravich
2022-11-03 16:32 ` Steven Rostedt
2022-11-02 14:20 ` Steven Rostedt
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