Created attachment 163063 [details] Patch

Comment on attachment 163063 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=163063&action=review > Source/WebKit2/DerivedSources.pri:148 > + win32: eval($${header_target}.commands = ($${QMAKE_MKDIR} $$toSystemPath($$dest_dir) 2>nul || echo>nul)) It looks like we use $${QMAKE_CHK_DIR_EXISTS} || $${QMAKE_MKDIR} in the rest of Qt's makefiles, perhaps stick with that?

Comment on attachment 163063 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=163063&action=review >> Source/WebKit2/DerivedSources.pri:148 >> + win32: eval($${header_target}.commands = ($${QMAKE_MKDIR} $$toSystemPath($$dest_dir) 2>nul || echo>nul)) > > It looks like we use $${QMAKE_CHK_DIR_EXISTS} || $${QMAKE_MKDIR} in the rest of Qt's makefiles, perhaps stick with that? The problem with that approach is that it doesn't work well with parallel rules that try to create the same directory ;( IOW there's a race condition between the check if the directory exists and making it. If you have two jobs trying to do the same thing, then both jobs determine simultaneously that the directory doesn't exist, both try to create the directory at the same time and only once succeeds. The second one will see mkdir aborting because the directory already exists. I tried removing the mkdir from this rule altogether and instead depend on the other generator that creates the directory also, but unfortunately when depending on such a symbol target nmake will always call it and thus always re-generate the file.

Comment on attachment 163063 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=163063&action=review >>> Source/WebKit2/DerivedSources.pri:148 >>> + win32: eval($${header_target}.commands = ($${QMAKE_MKDIR} $$toSystemPath($$dest_dir) 2>nul || echo>nul)) >> >> It looks like we use $${QMAKE_CHK_DIR_EXISTS} || $${QMAKE_MKDIR} in the rest of Qt's makefiles, perhaps stick with that? > > The problem with that approach is that it doesn't work well with parallel rules that try to create the same directory ;( > > IOW there's a race condition between the check if the directory exists and making it. If you have two jobs trying to do the same thing, then > both jobs determine simultaneously that the directory doesn't exist, both try to create the directory at the same time and only once succeeds. The > second one will see mkdir aborting because the directory already exists. > > I tried removing the mkdir from this rule altogether and instead depend on the other generator that creates the directory also, but unfortunately when > depending on such a symbol target nmake will always call it and thus always re-generate the file. Ouch! You're right, that will not be pretty. Wonder why Qt gets away with that though.

Comment on attachment 163063 [details] Patch Clearing flags on attachment: 163063 Committed r128045: <http://trac.webkit.org/changeset/128045>

All reviewed patches have been landed. Closing bug.