<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">If the documentation is true then it is essentially useless in general. Typical MS. On the other hand, several MS sources on the Web claim that it *is* atomic. Perhaps they should figure out what they really mean.<div><br></div><div><div apple-content-edited="true"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; 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font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div><font class="Apple-style-span" color="#0000FF"><font class="Apple-style-span" face="Gill Sans"><span class="Apple-style-span" style="color: rgb(0, 0, 255); font-family: 'Gill Sans'; "><span class="Apple-style-span" style="color: rgb(0, 0, 255); font-family: 'Gill Sans'; ">Antony Hosking</span></span></font></font><font class="Apple-style-span" face="Gill Sans"><span class="Apple-style-span" style="font-family: 'Gill Sans'; "><span class="Apple-style-span" style="font-family: 'Gill Sans'; "><span class="Apple-converted-space"> </span>|<span class="Apple-converted-space"> </span></span></span><span class="Apple-style-span" style="font-family: 'Gill Sans'; "><span class="Apple-style-span" style="font-family: 'Gill Sans'; ">Associate Professor</span></span><span class="Apple-style-span" style="font-family: 'Gill Sans'; "><span class="Apple-style-span" style="font-family: 'Gill Sans'; "> | Computer Science | Purdue University</span></span></font></div><div><font class="Apple-style-span" face="GillSans-Light"><span class="Apple-style-span" style="font-family: GillSans-Light; ">305 N. University Street | West Lafayette | IN 47907 | USA</span></font></div><div><font class="Apple-style-span" color="#0000FF" face="Gill Sans"><span class="Apple-style-span" style="color: rgb(0, 0, 255); font-family: 'Gill Sans'; "><span class="Apple-style-span" style="color: rgb(0, 0, 255); font-family: 'Gill Sans'; ">Office</span></span></font><font class="Apple-style-span" face="GillSans-Light"><span class="Apple-style-span" style="font-family: GillSans-Light; "><span class="Apple-style-span" style="font-family: GillSans-Light; "> +1 765 494 6001 |<span class="Apple-converted-space"> </span></span></span></font><font class="Apple-style-span" color="#0000FF" face="Gill Sans"><span class="Apple-style-span" style="color: rgb(0, 0, 255); font-family: 'Gill Sans'; "><span class="Apple-style-span" style="color: rgb(0, 0, 255); font-family: 'Gill Sans'; ">Mobile</span></span></font><font class="Apple-style-span" face="GillSans-Light"><span class="Apple-style-span" style="font-family: GillSans-Light; "><span class="Apple-style-span" style="font-family: GillSans-Light; "><span class="Apple-converted-space"> </span>+1 765 427 5484</span></span></font></div><div><font class="Apple-style-span" face="GillSans-Light"><br class="khtml-block-placeholder"></font></div></span></span></span></span></span></span></span><br class="Apple-interchange-newline"></span></div></span></div></span><br class="Apple-interchange-newline"> </div><br><div><div>On 29 Sep 2009, at 16:12, Jay K wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div class="hmmessage" style="font-size: 10pt; font-family: Verdana; ">SignalObjectAndWait is widely mentioned as important to implementing condition variables on Win32, however it is documented as not being atomic.<br>Search the web:<br><a href="http://msdn.microsoft.com/en-us/library/ms686293(VS.85).aspx">http://msdn.microsoft.com/en-us/library/ms686293(VS.85).aspx</a><br> <br>"Note that the "signal" and "wait" are not guaranteed to be performed as an atomic operation. Threads executing on other processors can observe the signaled state of the first object before the thread calling<span class="Apple-converted-space"> </span><strong>SignalObjectAndWait</strong><span class="Apple-converted-space"> </span>begins its wait on the second object."<br> <br>So it isn't useful, right?<br> <br>Thanks,<br> - Jay<br><br> <br><hr id="stopSpelling">From:<span class="Apple-converted-space"> </span><a href="mailto:hosking@cs.purdue.edu">hosking@cs.purdue.edu</a><br>To:<span class="Apple-converted-space"> </span><a href="mailto:m3devel@elegosoft.com">m3devel@elegosoft.com</a><br>Date: Tue, 29 Sep 2009 13:54:48 -0400<br>Subject: [M3devel] Win32 threads<br><br><div>I believe that the hangs we are seeing are because of the race present in AlertWait, which permit a thread to miss seeing an alert before waiting on the condition. We want the thread only to wait if there has been no alert. Unfortunately, the alert is only protected by the global mutex, which must be release before waiting. Currently, we release the mutex, then wait, with the resulting race. This requires a more complicated handshake than currently implemented. Perhaps using SignalObjectAndWait instead as well as a Win32 mutex on each thread. Similarly to ThreadPThread.m3.</div><div><br></div><div><br></div><div><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><div style="word-wrap: break-word; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><div style="word-wrap: break-word; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><span class="ecxApple-style-span" style="text-transform: none; text-indent: 0px; border-collapse: separate; font: normal normal normal 12px/normal Helvetica; white-space: normal; letter-spacing: normal; color: rgb(0, 0, 0); word-spacing: 0px; "><div><font class="ecxApple-style-span" color="#0000ff"><font class="ecxApple-style-span" face="Gill Sans"><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; color: rgb(0, 0, 255); "><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; color: rgb(0, 0, 255); ">Antony Hosking</span></span></font></font><font class="ecxApple-style-span" face="Gill Sans"><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; "><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; "><span class="ecxApple-converted-space"> </span>|<span class="ecxApple-converted-space"> </span></span></span><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; "><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; ">Associate Professor</span></span><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; "><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; "> | Computer Science | Purdue University</span></span></font></div><div><font class="ecxApple-style-span" face="GillSans-Light"><span class="ecxApple-style-span" style="font-family: GillSans-Light; ">305 N. University Street | West Lafayette | IN 47907 | USA</span></font></div><div><font class="ecxApple-style-span" color="#0000ff" face="Gill Sans"><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; color: rgb(0, 0, 255); "><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; color: rgb(0, 0, 255); ">Office</span></span></font><font class="ecxApple-style-span" face="GillSans-Light"><span class="ecxApple-style-span" style="font-family: GillSans-Light; "><span class="ecxApple-style-span" style="font-family: GillSans-Light; "> +1 765 494 6001 |<span class="ecxApple-converted-space"> </span></span></span></font><font class="ecxApple-style-span" color="#0000ff" face="Gill Sans"><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; color: rgb(0, 0, 255); "><span class="ecxApple-style-span" style="font-family: 'Gill Sans'; color: rgb(0, 0, 255); ">Mobile</span></span></font><font class="ecxApple-style-span" face="GillSans-Light"><span class="ecxApple-style-span" style="font-family: GillSans-Light; "><span class="ecxApple-style-span" style="font-family: GillSans-Light; "><span class="ecxApple-converted-space"> </span>+1 765 427 5484</span></span></font></div><div><font class="ecxApple-style-span" face="GillSans-Light"><br class="ecxkhtml-block-placeholder"></font></div></span></span></span></span></span></span></span><br class="ecxApple-interchange-newline"></span></div></span></div></span><br class="ecxApple-interchange-newline"></div><br></div></span><br class="Apple-interchange-newline"></blockquote></div><br></div></body></html>