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<p>This was done by design. The assumption is not that socket handles won't be greater than 0xFF, but rather that 255 mutexes are enough to share within one application space.</p>
<p><br></p>
<p>You are correct that different socket handles will use the same mutexes, which can cause lock contention, but deadlock should be impossible because within the calls only one mutex is ever held (and released) by a thread.</p>
<p><br></p>
<p>Cheers!</p>
<p>John</p>
<p><br></p>
<p>---</p>
<p>John Lane Schultz</p>
<p>Spread Concepts LLC</p>
<p>Phn: 443 838 2200 </p>
<p>Fax: 301 560 8875</p>
<p><br></p>
<p>Tuesday, June 17, 2008, 7:30:13 AM, you wrote:</p>
<p><br></p>
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<p><span class=rvts6>></span></p>
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<p><span class=rvts7>The mutex lock in “Sp.c” uses a dangerous assumption that doesn’t hold on Win32. The mbox will be assigned the opened win32 socket handle that could be greater than 0xFF, and for most time is.</span></p>
<p><span class=rvts7> </span></p>
<p><span class=rvts8>int</span><span class=rvts9> </span><span class=rvts10>SP_connect_timeout</span><span class=rvts9>( </span><span class=rvts8>const</span><span class=rvts9> </span><span class=rvts8>char</span><span class=rvts9> *</span><span class=rvts10>spread_name</span><span class=rvts9>, </span><span class=rvts8>const</span><span class=rvts9> </span><span class=rvts8>char</span><span class=rvts9> *</span><span class=rvts10>private_name</span><span class=rvts9>,</span></p>
<p><span class=rvts9> </span><span class=rvts8>int</span><span class=rvts9> </span><span class=rvts10>priority</span><span class=rvts9>, </span><span class=rvts8>int</span><span class=rvts9> </span><span class=rvts10>group_membership</span><span class=rvts9>, </span><span class=rvts10>mailbox</span><span class=rvts9> *</span><span class=rvts10>mbox</span><span class=rvts9>,</span></p>
<p><span class=rvts9> </span><span class=rvts8>char</span><span class=rvts9> *</span><span class=rvts10>private_group</span><span class=rvts9>, </span><span class=rvts10>sp_time</span><span class=rvts9> </span><span class=rvts10>time_out</span><span class=rvts9> )</span></p>
<p><span class=rvts9>{</span></p>
<p><span class=rvts7>.</span></p>
<p><span class=rvts10>s</span><span class=rvts9> = </span><span class=rvts10>socket</span><span class=rvts9>( </span><span class=rvts10>AF_UNIX</span><span class=rvts9>, </span><span class=rvts10>SOCK_STREAM</span><span class=rvts9>, 0 );</span></p>
<p><span class=rvts9>.</span></p>
<p><span class=rvts9>*</span><span class=rvts10>mbox</span><span class=rvts9> = </span><span class=rvts10>s</span><span class=rvts9>;</span></p>
<p><span class=rvts9>}</span></p>
<p><span class=rvts9> </span></p>
<p><span class=rvts7> </span></p>
<p><span class=rvts7>The following code is bad on win32, masking with 0xFF will generate different socket handles using the same mutex and could cause deadlock during multithreaded applications.</span></p>
<p><span class=rvts10> </span></p>
<p><span class=rvts8>int</span><span class=rvts9> </span><span class=rvts10>SP_scat_receive</span><span class=rvts9>( </span><span class=rvts10>mailbox</span><span class=rvts9> </span><span class=rvts10>mbox</span><span class=rvts9>, </span><span class=rvts10>service</span><span class=rvts9> *</span><span class=rvts10>service_type</span><span class=rvts9>, </span><span class=rvts8>char</span><span class=rvts9> </span><span class=rvts10>sender</span><span class=rvts9>[</span><span class=rvts10>MAX_GROUP_NAME</span><span class=rvts9>],</span></p>
<p><span class=rvts9> </span><span class=rvts8>int</span><span class=rvts9> </span><span class=rvts10>max_groups</span><span class=rvts9>, </span><span class=rvts8>int</span><span class=rvts9> *</span><span class=rvts10>num_groups</span><span class=rvts9>, </span><span class=rvts8>char</span><span class=rvts9> </span><span class=rvts10>groups</span><span class=rvts9>[][</span><span class=rvts10>MAX_GROUP_NAME</span><span class=rvts9>],</span></p>
<p><span class=rvts9> </span><span class=rvts10>int16</span><span class=rvts9> *</span><span class=rvts10>mess_type</span><span class=rvts9>, </span><span class=rvts8>int</span><span class=rvts9> *</span><span class=rvts10>endian_mismatch</span><span class=rvts9>,</span></p>
<p><span class=rvts9> </span><span class=rvts10>scatter</span><span class=rvts9> *</span><span class=rvts10>scat_mess</span><span class=rvts9> )</span></p>
<p><span class=rvts9>{</span></p>
<p><span class=rvts10>.</span></p>
<p><span class=rvts10>.</span></p>
<p><span class=rvts10>Mutex_lock</span><span class=rvts9>( &</span><span class=rvts10>Mbox_mutex</span><span class=rvts9>[</span><span class=rvts10>mbox</span><span class=rvts9> & </span><span class=rvts10>MAX_MUTEX_MASK</span><span class=rvts9>][1] );</span></p>
<p><span class=rvts9>.</span></p>
<p><span class=rvts9>.</span></p>
<p><span class=rvts9>}</span></p>
<p><span class=rvts9> </span></p>
<p><span class=rvts9> </span></p>
<p><span class=rvts7> </span></p>
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