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authorArnd Bergmann <arnd@arndb.de>2015-09-30 13:26:35 +0200
committerDavid S. Miller <davem@davemloft.net>2015-10-05 03:16:44 -0700
commit52f4f91893955c359885d022b2142e2326f020a1 (patch)
tree147ced546c99ee565357961bbf97a0e852cd7d72
parente253fb74d66428597bd272b2614e8564b882b14c (diff)
mwifiex: avoid gettimeofday in ba_threshold setting
mwifiex_get_random_ba_threshold() uses a complex homegrown implementation to generate a pseudo-random number from the current time as returned from do_gettimeofday(). This currently requires two 32-bit divisions plus a couple of other computations that are eventually discarded as only eight bits of the microsecond portion are used at all. We could replace this with a call to get_random_bytes(), but that might drain the entropy pool too fast if this is called for each packet. Instead, this patch converts it to use ktime_get_ns(), which is a bit faster than do_gettimeofday(), and then uses a similar algorithm as before, but in a way that takes both the nanosecond and second portion into account for slightly-more-but-still-not-very-random pseudorandom number. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Amitkumar Karwar <akarwar@marvell.com> Cc: Nishant Sarmukadam <nishants@marvell.com> Cc: Kalle Valo <kvalo@codeaurora.org> Cc: linux-wireless@vger.kernel.org Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/wireless/mwifiex/wmm.c15
1 files changed, 4 insertions, 11 deletions
diff --git a/drivers/net/wireless/mwifiex/wmm.c b/drivers/net/wireless/mwifiex/wmm.c
index 173d3663c2e0..878d358063dc 100644
--- a/drivers/net/wireless/mwifiex/wmm.c
+++ b/drivers/net/wireless/mwifiex/wmm.c
@@ -117,22 +117,15 @@ mwifiex_wmm_allocate_ralist_node(struct mwifiex_adapter *adapter, const u8 *ra)
*/
static u8 mwifiex_get_random_ba_threshold(void)
{
- u32 sec, usec;
- struct timeval ba_tstamp;
- u8 ba_threshold;
-
+ u64 ns;
/* setup ba_packet_threshold here random number between
* [BA_SETUP_PACKET_OFFSET,
* BA_SETUP_PACKET_OFFSET+BA_SETUP_MAX_PACKET_THRESHOLD-1]
*/
+ ns = ktime_get_ns();
+ ns += (ns >> 32) + (ns >> 16);
- do_gettimeofday(&ba_tstamp);
- sec = (ba_tstamp.tv_sec & 0xFFFF) + (ba_tstamp.tv_sec >> 16);
- usec = (ba_tstamp.tv_usec & 0xFFFF) + (ba_tstamp.tv_usec >> 16);
- ba_threshold = (((sec << 16) + usec) % BA_SETUP_MAX_PACKET_THRESHOLD)
- + BA_SETUP_PACKET_OFFSET;
-
- return ba_threshold;
+ return ((u8)ns % BA_SETUP_MAX_PACKET_THRESHOLD) + BA_SETUP_PACKET_OFFSET;
}
/*