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b58a36008b
The last RCU stall fix caused a massive throughput regression of the
hwrng on Raspberry Pi 0 - 3. hwrng_msleep doesn't sleep precisely enough
and usleep_range doesn't allow scheduling. So try to restore the
best possible throughput by introducing hwrng_yield which interruptable
sleeps for one jiffy.
Some performance measurements on Raspberry Pi 3B+ (arm64/defconfig):
sudo dd if=/dev/hwrng of=/dev/null count=1 bs=10000
cpu_relax ~138025 Bytes / sec
hwrng_msleep(1000) ~13 Bytes / sec
hwrng_yield ~2510 Bytes / sec
Fixes: 96cb9d0554 ("hwrng: bcm2835 - use hwrng_msleep() instead of cpu_relax()")
Link: https://lore.kernel.org/linux-arm-kernel/bc97ece5-44a3-4c4e-77da-2db3eb66b128@gmx.net/
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
69 lines
2.3 KiB
C
69 lines
2.3 KiB
C
/*
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Hardware Random Number Generator
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Please read Documentation/admin-guide/hw_random.rst for details on use.
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----------------------------------------------------------
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This software may be used and distributed according to the terms
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of the GNU General Public License, incorporated herein by reference.
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*/
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#ifndef LINUX_HWRANDOM_H_
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#define LINUX_HWRANDOM_H_
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#include <linux/completion.h>
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#include <linux/types.h>
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#include <linux/list.h>
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#include <linux/kref.h>
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/**
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* struct hwrng - Hardware Random Number Generator driver
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* @name: Unique RNG name.
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* @init: Initialization callback (can be NULL).
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* @cleanup: Cleanup callback (can be NULL).
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* @data_present: Callback to determine if data is available
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* on the RNG. If NULL, it is assumed that
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* there is always data available. *OBSOLETE*
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* @data_read: Read data from the RNG device.
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* Returns the number of lower random bytes in "data".
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* Must not be NULL. *OBSOLETE*
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* @read: New API. drivers can fill up to max bytes of data
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* into the buffer. The buffer is aligned for any type
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* and max is a multiple of 4 and >= 32 bytes.
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* @priv: Private data, for use by the RNG driver.
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* @quality: Estimation of true entropy in RNG's bitstream
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* (in bits of entropy per 1024 bits of input;
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* valid values: 1 to 1024, or 0 for maximum).
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*/
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struct hwrng {
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const char *name;
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int (*init)(struct hwrng *rng);
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void (*cleanup)(struct hwrng *rng);
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int (*data_present)(struct hwrng *rng, int wait);
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int (*data_read)(struct hwrng *rng, u32 *data);
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int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);
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unsigned long priv;
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unsigned short quality;
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/* internal. */
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struct list_head list;
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struct kref ref;
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struct completion cleanup_done;
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struct completion dying;
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};
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struct device;
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/** Register a new Hardware Random Number Generator driver. */
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extern int hwrng_register(struct hwrng *rng);
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extern int devm_hwrng_register(struct device *dev, struct hwrng *rng);
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/** Unregister a Hardware Random Number Generator driver. */
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extern void hwrng_unregister(struct hwrng *rng);
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extern void devm_hwrng_unregister(struct device *dve, struct hwrng *rng);
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extern long hwrng_msleep(struct hwrng *rng, unsigned int msecs);
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extern long hwrng_yield(struct hwrng *rng);
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#endif /* LINUX_HWRANDOM_H_ */
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