On 08/18/16 22:56, Herbert Xu wrote: > On Thu, Aug 18, 2016 at 10:49:47PM -0400, Theodore Ts'o wrote: >> >> That really depends on the system. We can't assume that people are >> using systems with a 100Hz clock interrupt. More often than not >> people are using tickless kernels these days. That's actually the >> problem with changing /dev/urandom to block until things are >> initialized. > > Couldn't we disable tickless until urandom has been seeded? In fact > perhaps we should accelerate the timer interrupt rate until it has > been seeded? > The biggest problem there is that the timer interrupt adds *no* entropy unless there is a source of asynchronicity in the system. On PCs, traditionally the timer has been run from a completely different crystal (14.31818 MHz) than the CPU, which is the ideal situation, but if they are run off the same crystal and run in lockstep, there is very little if anything there. On some systems, the timer may even *be* the only source of time, and the entropy truly is zero. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
