[Xen-changelog] [xen stable-4.2] common: make hypercall preemption checks consistent

[patchbot@xxxxxxx]

commit 584eb273dbd8f4325f419c0d1e160f1579c9efa4
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Apr 9 11:28:46 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Apr 9 11:28:46 2014 +0200

    common: make hypercall preemption checks consistent
    
    - never preempt on the first iteration (ensure forward progress)
    - do cheap checks first
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Tim Deegan <tim@xxxxxxx>
    Acked-by: Keir Fraser <keir@xxxxxxx>
    master commit: 8c0eed2cc8d8a2ccccdffe4c386b625b672dc12a
    master date: 2014-03-13 14:26:35 +0100
---
 xen/common/memory.c        |    9 +++++----
 xen/common/multicall.c     |    2 +-
 xen/drivers/char/console.c |    4 ++--
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index a515d1d..40f3e3e 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -59,7 +59,7 @@ static void increase_reservation(struct memop_args *a)
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -104,7 +104,7 @@ static void populate_physmap(struct memop_args *a)
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -242,7 +242,7 @@ static void decrease_reservation(struct memop_args *a)
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -355,7 +355,8 @@ static long 
memory_exchange(XEN_GUEST_HANDLE(xen_memory_exchange_t) arg)
           i < (exch.in.nr_extents >> in_chunk_order);
           i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != (exch.nr_exchanged >> in_chunk_order) &&
+             hypercall_preempt_check() )
         {
             exch.nr_exchanged = i << in_chunk_order;
             rcu_unlock_domain(d);
diff --git a/xen/common/multicall.c b/xen/common/multicall.c
index 6c1a9d7..697a3f3 100644
--- a/xen/common/multicall.c
+++ b/xen/common/multicall.c
@@ -38,7 +38,7 @@ do_multicall(
 
     for ( i = 0; !rc && i < nr_calls; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i && hypercall_preempt_check() )
             goto preempted;
 
         if ( unlikely(__copy_from_guest(&mcs->call, call_list, 1)) )
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index ef24f63..8579711 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -323,11 +323,11 @@ static 
DECLARE_SOFTIRQ_TASKLET(notify_dom0_con_ring_tasklet,
 static long guest_console_write(XEN_GUEST_HANDLE(char) buffer, int count)
 {
     char kbuf[128], *kptr;
-    int kcount;
+    int kcount = 0;
 
     while ( count > 0 )
     {
-        if ( hypercall_preempt_check() )
+        if ( kcount && hypercall_preempt_check() )
             return hypercall_create_continuation(
                 __HYPERVISOR_console_io, "iih",
                 CONSOLEIO_write, count, buffer);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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