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<p class="MsoNormal">Hello,<o:p></o:p></p>
<p class="MsoNormal">Please find attached a bug fix for a race condition on the mb_info_free callback.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Currently the code looks like the following (encoder/encoder.c): <o:p></o:p></p>
<p class="MsoNormal"> x264_threadslice_cond_broadcast( h, 2 );<o:p></o:p></p>
<p class="MsoNormal"> /* Do the first row of hpel, now that the previous slice is done */<o:p></o:p></p>
<p class="MsoNormal"> if( h->i_thread_idx > 0 )<o:p></o:p></p>
<p class="MsoNormal"> {<o:p></o:p></p>
<p class="MsoNormal"> x264_threadslice_cond_wait( h->thread[h->i_thread_idx-1], 2 );<o:p></o:p></p>
<p class="MsoNormal"> fdec_filter_row( h, h->i_threadslice_start + (1 << SLICE_MBAFF), 2 );<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"> [….] <o:p></o:p></p>
<p class="MsoNormal"> if( h->fdec->mb_info_free && (!h->param.b_sliced_threads || h->i_thread_idx == (h->param.i_threads-1)) )<o:p></o:p></p>
<p class="MsoNormal"> {<o:p></o:p></p>
<p class="MsoNormal"> h->fdec->mb_info_free( h->fdec->mb_info );<o:p></o:p></p>
<p class="MsoNormal"> h->fdec->mb_info = NULL;<o:p></o:p></p>
<p class="MsoNormal"> h->fdec->mb_info_free = NULL;<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Consider a case with at least three threads:<o:p></o:p></p>
<p class="MsoNormal">Thread 0 is lagging behind the other threads and still in the x264_macroblock_analyse(…) method.<o:p></o:p></p>
<p class="MsoNormal">Thread 1 is almost done and signals thread 2, then waits on thread 0 to signal in turn.<o:p></o:p></p>
<p class="MsoNormal">Thread 2 receives the green from thread 1 and goes on to call mb_info_free(…).<o:p></o:p></p>
<p class="MsoNormal">Thread 0 gets a SEGV if it checks for mb_info in the x264_macroblock_analyse(…).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A fix is for each thread to first wait on the previous one to broadcast pass 2 (except for thread 0) then broadcast.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Please find a patch implementing the above attached at the end of this email.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best,<o:p></o:p></p>
<p class="MsoNormal">Elias<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<br><br><br>NICE SRL, viale Monte Grappa 3/5, 20124 Milano, Italia, Registro delle Imprese di Milano Monza Brianza Lodi REA n. 2096882, Capitale Sociale: 10.329,14 EUR i.v., Cod. Fisc. e P.IVA 01133050052, Societa con Socio Unico<br><br><br>
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