[S390] pfault: cpu hotplug vs missing completion interrupts

On cpu hot remove a PFAULT CANCEL command is sent to the hypervisor
which in turn will cancel all outstanding pfault requests that have
been issued on that cpu (the same happens with a SIGP cpu reset).

The result is that we end up with uninterruptible processes where
the interrupt that would wake up these processes never arrives.

In order to solve this all processes which wait for a pfault
completion interrupt get woken up after a cpu hot remove. The worst
case that could happen is that they fault again and in turn need to
wait again.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 3 insertions, 0 deletions

diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index ef4555611013..edfbd17d7082 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -124,6 +124,7 @@ int main(void)
         DEFINE(__LC_LAST_UPDATE_TIMER, offsetof(struct _lowcore, last_update_timer));
         DEFINE(__LC_LAST_UPDATE_CLOCK, offsetof(struct _lowcore, last_update_clock));
         DEFINE(__LC_CURRENT, offsetof(struct _lowcore, current_task));
+        DEFINE(__LC_CURRENT_PID, offsetof(struct _lowcore, current_pid));
         DEFINE(__LC_THREAD_INFO, offsetof(struct _lowcore, thread_info));
         DEFINE(__LC_KERNEL_STACK, offsetof(struct _lowcore, kernel_stack));
         DEFINE(__LC_ASYNC_STACK, offsetof(struct _lowcore, async_stack));
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 1b67fc6ebdc2..0476174dfff5 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -212,6 +212,7 @@ __switch_to:
         lctl    %c4,%c4,__TASK_pid(%r3)         # load pid to control reg. 4
         lm      %r6,%r15,__SF_GPRS(%r15)        # load gprs of next task
         st      %r3,__LC_CURRENT                # store task struct of next
+        mvc     __LC_CURRENT_PID(4,%r0),__TASK_pid(%r3) # store pid of next
         st      %r5,__LC_THREAD_INFO            # store thread info of next
         ahi     %r5,STACK_SIZE                  # end of kernel stack of next
         st      %r5,__LC_KERNEL_STACK           # store end of kernel stack
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 9fd864563499..d61967e2eab0 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -220,6 +220,7 @@ __switch_to:
         lctl    %c4,%c4,__TASK_pid(%r3)         # load pid to control reg. 4
         lmg     %r6,%r15,__SF_GPRS(%r15)        # load gprs of next task
         stg     %r3,__LC_CURRENT                # store task struct of next
+        mvc     __LC_CURRENT_PID+4(4,%r0),__TASK_pid(%r3) # store pid of next
         stg     %r5,__LC_THREAD_INFO            # store thread info of next
         aghi    %r5,STACK_SIZE                  # end of kernel stack of next
         stg     %r5,__LC_KERNEL_STACK           # store end of kernel stack