diff options
| -rw-r--r-- | drivers/char/random.c | 42 |
1 files changed, 23 insertions, 19 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 364a8001a2b..dfe918a21e3 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -548,9 +548,9 @@ static void mix_pool_bytes(struct entropy_store *r, const void *in, struct fast_pool { __u32 pool[4]; unsigned long last; - unsigned short count; + unsigned char count; + unsigned char notimer_count; unsigned char rotate; - unsigned char last_timer_intr; }; /* @@ -850,15 +850,23 @@ void add_interrupt_randomness(int irq, int irq_flags) input[3] = ip >> 32; fast_mix(fast_pool, input); + if ((irq_flags & __IRQF_TIMER) == 0) + fast_pool->notimer_count++; - if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ)) - return; + if (cycles) { + if ((fast_pool->count < 64) && + !time_after(now, fast_pool->last + HZ)) + return; + } else { + /* CPU does not have a cycle counting register :-( */ + if (fast_pool->count < 64) + return; + } r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool; - if (!spin_trylock(&r->lock)) { - fast_pool->count--; + if (!spin_trylock(&r->lock)) return; - } + fast_pool->last = now; __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool)); @@ -874,19 +882,15 @@ void add_interrupt_randomness(int irq, int irq_flags) spin_unlock(&r->lock); /* - * If we don't have a valid cycle counter, and we see - * back-to-back timer interrupts, then skip giving credit for - * any entropy, otherwise credit 1 bit. + * If we have a valid cycle counter or if the majority of + * interrupts collected were non-timer interrupts, then give + * an entropy credit of 1 bit. Yes, this is being very + * conservative. */ - credit++; - if (cycles == 0) { - if (irq_flags & __IRQF_TIMER) { - if (fast_pool->last_timer_intr) - credit--; - fast_pool->last_timer_intr = 1; - } else - fast_pool->last_timer_intr = 0; - } + if (cycles || (fast_pool->notimer_count >= 32)) + credit++; + + fast_pool->count = fast_pool->notimer_count = 0; credit_entropy_bits(r, credit); } |