From: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org,
peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
alexander.shishkin@linux.intel.com, jolsa@redhat.com,
namhyung@kernel.org, linux-kernel@vger.kernel.org,
corbet@lwn.net, linux-doc@vger.kernel.org,
ananth@linux.vnet.ibm.com, alexis.berlemont@gmail.com,
naveen.n.rao@linux.vnet.ibm.com,
linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org,
linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com,
Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Subject: Re: [PATCH v5 09/10] Uprobes/sdt: Document about reference counter
Date: Tue, 3 Jul 2018 13:20:29 +0530 [thread overview]
Message-ID: <0110cd8a-9785-c761-e2a5-ba8ab92745e9@linux.ibm.com> (raw)
In-Reply-To: <20180702145444.GB65296@linux.vnet.ibm.com>
Hi Srikar,
On 07/02/2018 08:24 PM, Srikar Dronamraju wrote:
> * Ravi Bangoria <ravi.bangoria@linux.ibm.com> [2018-06-28 10:52:08]:
>
>> Reference counter gate the invocation of probe. If present,
>> by default reference count is 0. Kernel needs to increment
>> it before tracing the probe and decrement it when done. This
>> is identical to semaphore in Userspace Statically Defined
>> Tracepoints (USDT).
>>
>> Document usage of reference counter.
>>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
>> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> Unlike perf, this mechanism cannot detect ref count and depends on the
> users data. What happens if the user mistakenly provides a wrong location?
> I guess he can corrupt some other data structures?
Yes, if user is giving wrong ref_ctr_offset, uprobe infrastructure will
corrupt some user data.
>
> Hence I would think twice of advertising this mechanism. i.e keep this
> as an undocumented feature.
>
I don't mind.
Thanks,
Ravi
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next prev parent reply other threads:[~2018-07-03 7:51 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-28 5:21 [PATCH v5 00/10] Uprobes: Support SDT markers having reference count (semaphore) Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 01/10] Uprobes: Move uprobe structure to uprobe.h Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 02/10] Uprobes: Simplify uprobe_register() body Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 03/10] Uprobe: Change set_swbp definition Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 04/10] Uprobe: Change set_orig_insn definition Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 05/10] Uprobe: Change uprobe_write_opcode definition Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 06/10] Uprobes: Support SDT markers having reference count (semaphore) Ravi Bangoria
2018-06-28 19:51 ` Oleg Nesterov
2018-06-29 3:23 ` Ravi Bangoria
2018-07-01 21:09 ` Oleg Nesterov
2018-07-02 5:16 ` Ravi Bangoria
2018-07-02 18:01 ` Oleg Nesterov
2018-07-03 5:30 ` Ravi Bangoria
2018-07-03 6:16 ` Srikar Dronamraju
2018-07-03 7:43 ` Ravi Bangoria
2018-07-04 9:16 ` Srikar Dronamraju
2018-07-04 9:24 ` Ravi Bangoria
2018-07-03 8:11 ` Ravi Bangoria
2018-07-03 16:36 ` Oleg Nesterov
2018-07-03 17:25 ` Oleg Nesterov
2018-07-04 4:53 ` Ravi Bangoria
2018-07-10 15:25 ` Oleg Nesterov
2018-07-11 8:44 ` Ravi Bangoria
2018-07-11 9:52 ` Ravi Bangoria
2018-07-12 14:58 ` Oleg Nesterov
2018-07-12 19:53 ` Song Liu
2018-07-13 7:55 ` Ravi Bangoria
2018-07-13 23:50 ` Song Liu
2018-07-16 8:20 ` Ravi Bangoria
2018-07-16 8:51 ` Ravi Bangoria
2018-07-13 5:39 ` Ravi Bangoria
2018-07-04 4:49 ` Ravi Bangoria
2018-07-03 17:12 ` Oleg Nesterov
2018-07-03 18:23 ` Oleg Nesterov
2018-07-04 5:25 ` Ravi Bangoria
2018-07-02 16:01 ` Srikar Dronamraju
2018-07-02 18:05 ` Oleg Nesterov
2018-07-03 6:29 ` Ravi Bangoria
2018-07-03 19:26 ` Oleg Nesterov
2018-07-04 5:26 ` Ravi Bangoria
2018-07-04 6:07 ` Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 07/10] trace_uprobe/sdt: Prevent multiple reference counter for same uprobe Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 08/10] Uprobes/sdt: " Ravi Bangoria
2018-06-28 5:22 ` [PATCH v5 09/10] Uprobes/sdt: Document about reference counter Ravi Bangoria
2018-07-02 14:54 ` Srikar Dronamraju
2018-07-03 7:50 ` Ravi Bangoria [this message]
2018-06-28 5:22 ` [PATCH v5 10/10] perf probe: Support SDT markers having reference counter (semaphore) Ravi Bangoria
2018-07-02 14:45 ` Srikar Dronamraju
2018-07-02 14:57 ` Srikar Dronamraju
2018-07-03 8:00 ` Ravi Bangoria
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