4.9-stable patches

added patches:
	mark-hi-and-tasklet-softirq-synchronous.patch

diff --git a/queue-4.9/mark-hi-and-tasklet-softirq-synchronous.patch b/queue-4.9/mark-hi-and-tasklet-softirq-synchronous.patch
new file mode 100644 (file)
index 0000000..678b1ba
--- /dev/null
+++ b/queue-4.9/mark-hi-and-tasklet-softirq-synchronous.patch
@@ -0,0 +1,103 @@
+From 3c53776e29f81719efcf8f7a6e30cdf753bee94d Mon Sep 17 00:00:00 2001
+From: Linus Torvalds <torvalds@linux-foundation.org>
+Date: Mon, 8 Jan 2018 11:51:04 -0800
+Subject: Mark HI and TASKLET softirq synchronous
+
+From: Linus Torvalds <torvalds@linux-foundation.org>
+
+commit 3c53776e29f81719efcf8f7a6e30cdf753bee94d upstream.
+
+Way back in 4.9, we committed 4cd13c21b207 ("softirq: Let ksoftirqd do
+its job"), and ever since we've had small nagging issues with it.  For
+example, we've had:
+
+  1ff688209e2e ("watchdog: core: make sure the watchdog_worker is not deferred")
+  8d5755b3f77b ("watchdog: softdog: fire watchdog even if softirqs do not get to run")
+  217f69743681 ("net: busy-poll: allow preemption in sk_busy_loop()")
+
+all of which worked around some of the effects of that commit.
+
+The DVB people have also complained that the commit causes excessive USB
+URB latencies, which seems to be due to the USB code using tasklets to
+schedule USB traffic.  This seems to be an issue mainly when already
+living on the edge, but waiting for ksoftirqd to handle it really does
+seem to cause excessive latencies.
+
+Now Hanna Hawa reports that this issue isn't just limited to USB URB and
+DVB, but also causes timeout problems for the Marvell SoC team:
+
+ "I'm facing kernel panic issue while running raid 5 on sata disks
+  connected to Macchiatobin (Marvell community board with Armada-8040
+  SoC with 4 ARMv8 cores of CA72) Raid 5 built with Marvell DMA engine
+  and async_tx mechanism (ASYNC_TX_DMA [=y]); the DMA driver (mv_xor_v2)
+  uses a tasklet to clean the done descriptors from the queue"
+
+The latency problem causes a panic:
+
+  mv_xor_v2 f0400000.xor: dma_sync_wait: timeout!
+  Kernel panic - not syncing: async_tx_quiesce: DMA error waiting for transaction
+
+We've discussed simply just reverting the original commit entirely, and
+also much more involved solutions (with per-softirq threads etc).  This
+patch is intentionally stupid and fairly limited, because the issue
+still remains, and the other solutions either got sidetracked or had
+other issues.
+
+We should probably also consider the timer softirqs to be synchronous
+and not be delayed to ksoftirqd (since they were the issue with the
+earlier watchdog problems), but that should be done as a separate patch.
+This does only the tasklet cases.
+
+Reported-and-tested-by: Hanna Hawa <hannah@marvell.com>
+Reported-and-tested-by: Josef Griebichler <griebichler.josef@gmx.at>
+Reported-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
+Cc: Alan Stern <stern@rowland.harvard.edu>
+Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Cc: Eric Dumazet <edumazet@google.com>
+Cc: Ingo Molnar <mingo@kernel.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ kernel/softirq.c |   12 ++++++++----
+ 1 file changed, 8 insertions(+), 4 deletions(-)
+
+--- a/kernel/softirq.c
++++ b/kernel/softirq.c
+@@ -79,12 +79,16 @@ static void wakeup_softirqd(void)
+ 
+ /*
+  * If ksoftirqd is scheduled, we do not want to process pending softirqs
+- * right now. Let ksoftirqd handle this at its own rate, to get fairness.
++ * right now. Let ksoftirqd handle this at its own rate, to get fairness,
++ * unless we're doing some of the synchronous softirqs.
+  */
+-static bool ksoftirqd_running(void)
++#define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ))
++static bool ksoftirqd_running(unsigned long pending)
+ {
+       struct task_struct *tsk = __this_cpu_read(ksoftirqd);
+ 
++      if (pending & SOFTIRQ_NOW_MASK)
++              return false;
+       return tsk && (tsk->state == TASK_RUNNING);
+ }
+ 
+@@ -324,7 +328,7 @@ asmlinkage __visible void do_softirq(voi
+ 
+       pending = local_softirq_pending();
+ 
+-      if (pending && !ksoftirqd_running())
++      if (pending && !ksoftirqd_running(pending))
+               do_softirq_own_stack();
+ 
+       local_irq_restore(flags);
+@@ -351,7 +355,7 @@ void irq_enter(void)
+ 
+ static inline void invoke_softirq(void)
+ {
+-      if (ksoftirqd_running())
++      if (ksoftirqd_running(local_softirq_pending()))
+               return;
+ 
+       if (!force_irqthreads) {

diff --git a/queue-4.9/series b/queue-4.9/series
index 2ca2711a04bb9ee01bd57f8544d4756c58a2ad2e..49b496bd6129aba8071cae3913d78c26d702eb41 100644 (file)
--- a/queue-4.9/series
+++ b/queue-4.9/series
@@ -3,3 +3,4 @@ tpm-fix-race-condition-in-tpm_common_write.patch
 parisc-enable-config_mlongcalls-by-default.patch
 parisc-define-mb-and-add-memory-barriers-to-assembler-unlock-sequences.patch
 kasan-add-no_sanitize-attribute-for-clang-builds.patch
+mark-hi-and-tasklet-softirq-synchronous.patch