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Date:   Wed, 26 May 2021 13:44:56 +0200
From:   Jiri Olsa <jolsa@redhat.com>
To:     "Jin, Yao" <yao.jin@linux.intel.com>
Cc:     acme@kernel.org, jolsa@kernel.org, peterz@infradead.org,
        mingo@redhat.com, alexander.shishkin@linux.intel.com,
        Linux-kernel@vger.kernel.org, ak@linux.intel.com,
        kan.liang@intel.com, yao.jin@intel.com
Subject: Re: [PATCH v1 4/5] perf mem: Support record for hybrid platform
Message-ID: <YK40uLOZC+4qGMl3@krava>
References: <20210520070040.710-1-yao.jin@linux.intel.com>
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 <aa5f0be5-c939-3c26-9d2a-3a073449bf98@linux.intel.com>
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On Wed, May 26, 2021 at 09:51:34AM +0800, Jin, Yao wrote:
> Hi Jiri,
> 
> On 5/25/2021 3:39 PM, Jin, Yao wrote:
> > Hi Jiri,
> > 
> > > > > ????? rec_argv = calloc(rec_argc + 1, sizeof(char *));
> > > > > ????? if (!rec_argv)
> > > > > ????????? return -1;
> > > > > +??? /*
> > > > > +???? * Save the allocated event name strings.
> > > > > +???? */
> > > > > +??? rec_tmp = calloc(rec_argc + 1, sizeof(char *));
> > > > > +??? if (!rec_tmp) {
> > > > > +??????? free(rec_argv);
> > > > > +??????? return -1;
> > > > > +??? }
> > > > 
> > > > why not do strdup on all of them and always call free instead?
> > > > that would get rid of the rec_tmp and tmp_nr
> > > > 
> > > 
> > > That is also one method. Let me try it.
> > > 
> > 
> > If we do strdup on all of them, such as,
> > 
> >  ????if (e->record)
> >  ??????? rec_argv[i++] = strdup("-W");
> > 
> >  ????rec_argv[i++] = strdup("-d");
> > 
> >  ????if (mem->phys_addr)
> >  ??????? rec_argv[i++] = strdup("--phys-data");
> >  ????....
> > 
> > That looks too much strdup used here. So I choose to use a rec_tmp[] to
> > record the allocated string and free them before exit the function.
> > 
> > Or we record the start index and end index in rec_argv[] for the
> > allocated event string, use strdup on them and call free before exit the
> > function.
> > 
> 
> This method looks also not OK.
> 
> The rec_argv[] is changed in cmd_record() for some complex command lines.
> 
> For example,
> 
> ./perf mem record -- ./memtest -R0d -b2000 -d64 -n100
> 
> Before cmd_record(), rec_argv[3] = "-e".
> After cmd_record(), rec_argv[3] = "-d64"
> 
> Even we do strdup on all of rec_argv[], but the entries are probably changed
> in cmd_record(), so we can't free the entries at the end of __cmd_record().
> 
> Maybe we have to use the original way which just records the allocated event
> string to a temporary array and free the whole array at the end of
> __cmd_record().
> 
> What do you think?

ok, it was worth to try ;-)

thanks,
jirka