linux-kernel - Re: [PATCH 0/7] Uprobes: Support SDT markers having reference count (semaphore)

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Message-Id: <df7e41ee-87b3-1f95-3fde-a7deadfcab7a@linux.ibm.com>
Date:   Thu, 21 Jun 2018 08:05:38 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     oleg@...hat.com, srikar@...ux.vnet.ibm.com, mhiramat@...nel.org,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org, corbet@....net,
        linux-doc@...r.kernel.org, ananth@...ux.vnet.ibm.com,
        alexis.berlemont@...il.com, naveen.n.rao@...ux.vnet.ibm.com,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH 0/7] Uprobes: Support SDT markers having reference count
 (semaphore)



On 06/20/2018 10:07 PM, Steven Rostedt wrote:
> On Wed,  6 Jun 2018 14:03:37 +0530
> Ravi Bangoria <ravi.bangoria@...ux.ibm.com> wrote:
> 
>> Why RFC again:
>>
>> This series is different from earlier versions[1]. Earlier series
>> implemented this feature in trace_uprobe while this has implemented
>> the logic in core uprobe. Few reasons for this:
>>  1. One of the major reason was the deadlock between uprobe_lock and
>>  mm->mmap inside trace_uprobe_mmap(). That deadlock was not easy to fix
>>  because mm->mmap is not in control of trace_uprobe_mmap() and it has
>>  to take uprobe_lock to loop over trace_uprobe list. More details can
>>  be found at[2]. With this new approach, there are no deadlocks found
>>  so far.
>>  2. Many of the core uprobe function and data-structures needs to be
>>  exported to make earlier implementation simple. With this new approach,
>>  reference counter logic is been implemented in core uprobe and thus
>>  no need to export anything.
> 
> 
> A quick scan of the patches, I don't see anything controversial with
> them. Unless others have any qualms about it, I say repost as non RFC,
> and we can start doing a more thorough review.

Yes, I've posted it: https://lkml.org/lkml/2018/6/19/1324

I've copied you as well :) Please have a look.

Thanks,
Ravi