Messages in this thread | | | From | "Bernard Normier" <> | Subject | Re: Concurrent access to /dev/urandom | Date | Sat, 27 Nov 2004 16:15:36 -0500 |
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> >As long as I serialize access to /dev/urandom, I get different values. >>However, with concurrent access to /dev/urandom, I quickly get duplicate > > How do you concurrently read from urandom? That's only possible with 2 or > more > CPUs, and even then, I hope that the urandom chardev has some spinlock. > As shown in the code included in my first e-mail, each thread simply open("/dev/urandom", O_RDONLY), use read(2) to read 16 bytes, and then close the file descriptor. Duplicates appear quickly on: single CPU with HT, dual CPU without HT, and dual CPU with HT (all with smp kernels) But not on a lower end single CPU without HT (2.6.8-1.521 non-smp).
>>#include <pthread.h> >>[...] > > Rule of thumb: Post the smallest possible code that shows the problem. Will do next time!
Bernard
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