Patch "MIPS: pm-cps: Drop manual cache-line alignment of ready_count" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    MIPS: pm-cps: Drop manual cache-line alignment of ready_count

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-pm-cps-drop-manual-cache-line-alignment-of-ready_count.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 161c51ccb7a6faf45ffe09aa5cf1ad85ccdad503 Mon Sep 17 00:00:00 2001
From: Paul Burton <paul.burton@imgtec.com>
Date: Thu, 2 Mar 2017 14:02:40 -0800
Subject: MIPS: pm-cps: Drop manual cache-line alignment of ready_count

From: Paul Burton <paul.burton@imgtec.com>

commit 161c51ccb7a6faf45ffe09aa5cf1ad85ccdad503 upstream.

We allocate memory for a ready_count variable per-CPU, which is accessed
via a cached non-coherent TLB mapping to perform synchronisation between
threads within the core using LL/SC instructions. In order to ensure
that the variable is contained within its own data cache line we
allocate 2 lines worth of memory & align the resulting pointer to a line
boundary. This is however unnecessary, since kmalloc is guaranteed to
return memory which is at least cache-line aligned (see
ARCH_DMA_MINALIGN). Stop the redundant manual alignment.

Besides cleaning up the code & avoiding needless work, this has the side
effect of avoiding an arithmetic error found by Bryan on 64 bit systems
due to the 32 bit size of the former dlinesz. This led the ready_count
variable to have its upper 32b cleared erroneously for MIPS64 kernels,
causing problems when ready_count was later used on MIPS64 via cpuidle.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: 3179d37ee1ed ("MIPS: pm-cps: add PM state entry code for CPS systems")
Reported-by: Bryan O'Donoghue <bryan.odonoghue@imgtec.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@imgtec.com>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15383/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/pm-cps.c |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

--- a/arch/mips/kernel/pm-cps.c
+++ b/arch/mips/kernel/pm-cps.c
@@ -55,7 +55,6 @@ DECLARE_BITMAP(state_support, CPS_PM_STA
  * state. Actually per-core rather than per-CPU.
  */
 static DEFINE_PER_CPU_ALIGNED(u32*, ready_count);
-static DEFINE_PER_CPU_ALIGNED(void*, ready_count_alloc);
 
 /* Indicates online CPUs coupled with the current CPU */
 static DEFINE_PER_CPU_ALIGNED(cpumask_t, online_coupled);
@@ -625,7 +624,6 @@ static int __init cps_gen_core_entries(u
 {
 	enum cps_pm_state state;
 	unsigned core = cpu_data[cpu].core;
-	unsigned dlinesz = cpu_data[cpu].dcache.linesz;
 	void *entry_fn, *core_rc;
 
 	for (state = CPS_PM_NC_WAIT; state < CPS_PM_STATE_COUNT; state++) {
@@ -645,16 +643,11 @@ static int __init cps_gen_core_entries(u
 	}
 
 	if (!per_cpu(ready_count, core)) {
-		core_rc = kmalloc(dlinesz * 2, GFP_KERNEL);
+		core_rc = kmalloc(sizeof(u32), GFP_KERNEL);
 		if (!core_rc) {
 			pr_err("Failed allocate core %u ready_count\n", core);
 			return -ENOMEM;
 		}
-		per_cpu(ready_count_alloc, core) = core_rc;
-
-		/* Ensure ready_count is aligned to a cacheline boundary */
-		core_rc += dlinesz - 1;
-		core_rc = (void *)((unsigned long)core_rc & ~(dlinesz - 1));
 		per_cpu(ready_count, core) = core_rc;
 	}
 


Patches currently in stable-queue which might be from paul.burton@imgtec.com are

queue-4.4/mips-pm-cps-drop-manual-cache-line-alignment-of-ready_count.patch
queue-4.4/mips-fix-irq-tracing-lockdep-when-rescheduling.patch