14.09.2017, 10:22, "Sami Nurmenniemi" <sami.nurmenni...@qt.io>: > Hi, > > Commit 120ecc976fc3d5504d234702f68c2ad3898b77a4 changes default behavior of > QRandomGenerator to use getentropy instead of /dev/urandom. This causes > problems for device boot times when using QRandomGenerator in the boot > sequence. As the commit message itself states "What's more, the glibc > implementation blocks until entropy is available on early boot". Depending on > the hw + kernel configuration of the device, this can increase boot time by > more than a minute. For example in the Boot2Qt image qdbd and qtlauncher demo > now block until the nonblocking pool is initialized. See QTBUG-63188. > > What do you suggest for working around this problem? > 1. Disable feature "getentropy" from Boot2Qt builds > - This is the behavior in Qt < 5.10.x > - Only difference in the entropy of randomness is in the early boot > 2. Add "rng-tools" to the image for inputting entropy to the kernel > - Speeds up initialization of nonblocking pool > - On devices with HW random generator, this adds real entropy to the kernel > pool > - On devices without HW random generator, this adds bad entropy from > /dev/urandom to the kernel pool > 3. Setting QT_HASH_SEED for the affected processes > - Not a good solution IMO
Why? Is hash randomization really important in your case? Also, you may want to replace QHash with a different data structure in your boot code. > - It seems code using this in qhash.cpp is the actual reason for the blocked > processes (originated from QDebug) > 4. Something else? > > Best Regards, > Sami Nurmenniemi > > , > > _______________________________________________ > Development mailing list > Development@qt-project.org > http://lists.qt-project.org/mailman/listinfo/development -- Regards, Konstantin _______________________________________________ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
