[app_server] deadlock on font change

[diver]

I can reproduce it only on real hw now. After i compile recent haiku sources and boot it, i set resolution to 1152*864@77.1 Hzafter that i lauched Fonts from Terminal and changed default to DjVu font (as it support cyrillic glyphs), a second later app_server freezed.

[axeld]

Bug #893 is a duplicate of this one.

[jackburton]

Axel, I might be wrong, but the case for AS_SET_SYSTEM_FONT, in ServerApp, looks suspicious.

There we acquire the gFontManager lock, then we instantiate a LockedDesktopSettings, which in turn tries to acquire the gFontManager lock again (in DesktopSettingsPrivate::_Load()).

[axeld]

While AS_SET_SYSTEM_FONT was indeed to blame, DesktopSettingsPrivate::_Load() was not called in this context. However, ServerFont::SetFamilyAndStyle() implicitly locks the font manager, and thus, it dead locked with the case above: you must not hold the font manager lock when locking the desktop. Fixed in r19051.

[diver]

Happens again 2 times in r22510, reopening.

[diver]

I could reproduce this deadlock by changing Bold Font 2-20 times.