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Annotate that get_cyclecount() can be expensive on some platforms,

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which juxtaposes nicely with the comment just above on how the
harvest function must be cheap.
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rwatson 2004-10-18 19:29:13 +00:00
parent d7592a9bb7
commit 7b853afb00
1 changed files with 4 additions and 0 deletions
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sys/dev/random/harvest.c
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@ -77,6 +77,10 @@ random_yarrow_deinit_harvester(void)
* not do anything slow in here! * not do anything slow in here!
* Implemented as in indirect call to allow non-inclusion of * Implemented as in indirect call to allow non-inclusion of
* the entropy device. * the entropy device.
*
* XXXRW: get_cyclecount() is cheap on most modern hardware, where cycle
* counters are built in, but on older hardware it will do a real time clock
* read which can be quite expensive.
*/ */
void void
random_harvest(void *entropy, u_int count, u_int bits, u_int frac, random_harvest(void *entropy, u_int count, u_int bits, u_int frac,