5.4-stable patches

added patches:
	random-use-expired-timer-rather-than-wq-for-mixing-fast-pool.patch

diff --git a/queue-5.4/random-use-expired-timer-rather-than-wq-for-mixing-fast-pool.patch b/queue-5.4/random-use-expired-timer-rather-than-wq-for-mixing-fast-pool.patch
new file mode 100644 (file)
index 0000000..6903311
--- /dev/null
+++ b/queue-5.4/random-use-expired-timer-rather-than-wq-for-mixing-fast-pool.patch
@@ -0,0 +1,130 @@
+From 748bc4dd9e663f23448d8ad7e58c011a67ea1eca Mon Sep 17 00:00:00 2001
+From: "Jason A. Donenfeld" <Jason@zx2c4.com>
+Date: Thu, 22 Sep 2022 18:46:04 +0200
+Subject: random: use expired timer rather than wq for mixing fast pool
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Jason A. Donenfeld <Jason@zx2c4.com>
+
+commit 748bc4dd9e663f23448d8ad7e58c011a67ea1eca upstream.
+
+Previously, the fast pool was dumped into the main pool periodically in
+the fast pool's hard IRQ handler. This worked fine and there weren't
+problems with it, until RT came around. Since RT converts spinlocks into
+sleeping locks, problems cropped up. Rather than switching to raw
+spinlocks, the RT developers preferred we make the transformation from
+originally doing:
+
+    do_some_stuff()
+    spin_lock()
+    do_some_other_stuff()
+    spin_unlock()
+
+to doing:
+
+    do_some_stuff()
+    queue_work_on(some_other_stuff_worker)
+
+This is an ordinary pattern done all over the kernel. However, Sherry
+noticed a 10% performance regression in qperf TCP over a 40gbps
+InfiniBand card. Quoting her message:
+
+> MT27500 Family [ConnectX-3] cards:
+> Infiniband device 'mlx4_0' port 1 status:
+> default gid: fe80:0000:0000:0000:0010:e000:0178:9eb1
+> base lid: 0x6
+> sm lid: 0x1
+> state: 4: ACTIVE
+> phys state: 5: LinkUp
+> rate: 40 Gb/sec (4X QDR)
+> link_layer: InfiniBand
+>
+> Cards are configured with IP addresses on private subnet for IPoIB
+> performance testing.
+> Regression identified in this bug is in TCP latency in this stack as reported
+> by qperf tcp_lat metric:
+>
+> We have one system listen as a qperf server:
+> [root@yourQperfServer ~]# qperf
+>
+> Have the other system connect to qperf server as a client (in this
+> case, it’s X7 server with Mellanox card):
+> [root@yourQperfClient ~]# numactl -m0 -N0 qperf 20.20.20.101 -v -uu -ub --time 60 --wait_server 20 -oo msg_size:4K:1024K:*2 tcp_lat
+
+Rather than incur the scheduling latency from queue_work_on, we can
+instead switch to running on the next timer tick, on the same core. This
+also batches things a bit more -- once per jiffy -- which is okay now
+that mix_interrupt_randomness() can credit multiple bits at once.
+
+Reported-by: Sherry Yang <sherry.yang@oracle.com>
+Tested-by: Paul Webb <paul.x.webb@oracle.com>
+Cc: Sherry Yang <sherry.yang@oracle.com>
+Cc: Phillip Goerl <phillip.goerl@oracle.com>
+Cc: Jack Vogel <jack.vogel@oracle.com>
+Cc: Nicky Veitch <nicky.veitch@oracle.com>
+Cc: Colm Harrington <colm.harrington@oracle.com>
+Cc: Ramanan Govindarajan <ramanan.govindarajan@oracle.com>
+Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Cc: Dominik Brodowski <linux@dominikbrodowski.net>
+Cc: Tejun Heo <tj@kernel.org>
+Cc: Sultan Alsawaf <sultan@kerneltoast.com>
+Cc: stable@vger.kernel.org
+Fixes: 58340f8e952b ("random: defer fast pool mixing to worker")
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/char/random.c |   18 +++++++++++-------
+ 1 file changed, 11 insertions(+), 7 deletions(-)
+
+--- a/drivers/char/random.c
++++ b/drivers/char/random.c
+@@ -893,17 +893,20 @@ struct fast_pool {
+       unsigned long pool[4];
+       unsigned long last;
+       unsigned int count;
+-      struct work_struct mix;
++      struct timer_list mix;
+ };
+ 
++static void mix_interrupt_randomness(struct timer_list *work);
++
+ static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
+ #ifdef CONFIG_64BIT
+ #define FASTMIX_PERM SIPHASH_PERMUTATION
+-      .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 }
++      .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 },
+ #else
+ #define FASTMIX_PERM HSIPHASH_PERMUTATION
+-      .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 }
++      .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 },
+ #endif
++      .mix = __TIMER_INITIALIZER(mix_interrupt_randomness, 0)
+ };
+ 
+ /*
+@@ -945,7 +948,7 @@ int __cold random_online_cpu(unsigned in
+ }
+ #endif
+ 
+-static void mix_interrupt_randomness(struct work_struct *work)
++static void mix_interrupt_randomness(struct timer_list *work)
+ {
+       struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix);
+       /*
+@@ -999,10 +1002,11 @@ void add_interrupt_randomness(int irq)
+       if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ))
+               return;
+ 
+-      if (unlikely(!fast_pool->mix.func))
+-              INIT_WORK(&fast_pool->mix, mix_interrupt_randomness);
+       fast_pool->count |= MIX_INFLIGHT;
+-      queue_work_on(raw_smp_processor_id(), system_highpri_wq, &fast_pool->mix);
++      if (!timer_pending(&fast_pool->mix)) {
++              fast_pool->mix.expires = jiffies;
++              add_timer_on(&fast_pool->mix, raw_smp_processor_id());
++      }
+ }
+ EXPORT_SYMBOL_GPL(add_interrupt_randomness);
+ 

diff --git a/queue-5.4/series b/queue-5.4/series
index 67590835c212fc420a20fbf130b2017f44291f58..b11e475d43248d75792da8980c17adb39088bb6e 100644 (file)
--- a/queue-5.4/series
+++ b/queue-5.4/series
@@ -26,3 +26,4 @@ scsi-stex-properly-zero-out-the-passthrough-command-structure.patch
 usb-serial-qcserial-add-new-usb-id-for-dell-branded-em7455.patch
 random-restore-o_nonblock-support.patch
 random-avoid-reading-two-cache-lines-on-irq-randomness.patch
+random-use-expired-timer-rather-than-wq-for-mixing-fast-pool.patch