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authorHeiko Carstens <heiko.carstens@de.ibm.com>2011-05-23 10:24:34 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2011-05-23 10:24:29 +0200
commitf2db2e6cb3f5f766cbb3788af44705685ff2445a (patch)
tree11fbf5522f332e13f9bfb6cf4552513e4d865003
parentb456d94a9757db54eca4677c1b3a13e7170c9bb3 (diff)
[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>
-rw-r--r--arch/s390/include/asm/lowcore.h4
-rw-r--r--arch/s390/include/asm/processor.h1
-rw-r--r--arch/s390/kernel/asm-offsets.c1
-rw-r--r--arch/s390/kernel/entry.S1
-rw-r--r--arch/s390/kernel/entry64.S1
-rw-r--r--arch/s390/mm/fault.c89
6 files changed, 71 insertions, 26 deletions
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index b8624d53c37..228cf0b295d 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -124,7 +124,7 @@ struct _lowcore {
/* Address space pointer. */
__u32 kernel_asce; /* 0x02ac */
__u32 user_asce; /* 0x02b0 */
- __u8 pad_0x02b4[0x02b8-0x02b4]; /* 0x02b4 */
+ __u32 current_pid; /* 0x02b4 */
/* SMP info area */
__u32 cpu_nr; /* 0x02b8 */
@@ -255,7 +255,7 @@ struct _lowcore {
/* Address space pointer. */
__u64 kernel_asce; /* 0x0310 */
__u64 user_asce; /* 0x0318 */
- __u8 pad_0x0320[0x0328-0x0320]; /* 0x0320 */
+ __u64 current_pid; /* 0x0320 */
/* SMP info area */
__u32 cpu_nr; /* 0x0328 */
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 2c79b641627..1300c302533 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -84,6 +84,7 @@ struct thread_struct {
struct per_event per_event; /* Cause of the last PER trap */
/* pfault_wait is used to block the process on a pfault event */
unsigned long pfault_wait;
+ struct list_head list;
};
typedef struct thread_struct thread_struct;
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index ef455561101..edfbd17d708 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 1b67fc6ebdc..0476174dfff 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 9fd86456349..d61967e2eab 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
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 177745c520c..1ca65647832 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -466,7 +466,7 @@ typedef struct {
int pfault_init(void)
{
pfault_refbk_t refbk =
- { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
+ { 0x258, 0, 5, 2, __LC_CURRENT_PID, 1ULL << 48, 1ULL << 48,
__PF_RES_FIELD };
int rc;
@@ -498,11 +498,15 @@ void pfault_fini(void)
: : "a" (&refbk), "m" (refbk) : "cc");
}
+static DEFINE_SPINLOCK(pfault_lock);
+static LIST_HEAD(pfault_list);
+
static void pfault_interrupt(unsigned int ext_int_code,
unsigned int param32, unsigned long param64)
{
struct task_struct *tsk;
__u16 subcode;
+ pid_t pid;
/*
* Get the external interruption subcode & pfault
@@ -514,44 +518,79 @@ static void pfault_interrupt(unsigned int ext_int_code,
if ((subcode & 0xff00) != __SUBCODE_MASK)
return;
kstat_cpu(smp_processor_id()).irqs[EXTINT_PFL]++;
-
- /*
- * Get the token (= address of the task structure of the affected task).
- */
-#ifdef CONFIG_64BIT
- tsk = (struct task_struct *) param64;
-#else
- tsk = (struct task_struct *) param32;
-#endif
-
+ if (subcode & 0x0080) {
+ /* Get the token (= pid of the affected task). */
+ pid = sizeof(void *) == 4 ? param32 : param64;
+ rcu_read_lock();
+ tsk = find_task_by_pid_ns(pid, &init_pid_ns);
+ if (tsk)
+ get_task_struct(tsk);
+ rcu_read_unlock();
+ if (!tsk)
+ return;
+ } else {
+ tsk = current;
+ }
+ spin_lock(&pfault_lock);
if (subcode & 0x0080) {
/* signal bit is set -> a page has been swapped in by VM */
- if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
+ if (tsk->thread.pfault_wait == 1) {
/* Initial interrupt was faster than the completion
* interrupt. pfault_wait is valid. Set pfault_wait
* back to zero and wake up the process. This can
* safely be done because the task is still sleeping
* and can't produce new pfaults. */
tsk->thread.pfault_wait = 0;
+ list_del(&tsk->thread.list);
wake_up_process(tsk);
- put_task_struct(tsk);
+ } else {
+ /* Completion interrupt was faster than initial
+ * interrupt. Set pfault_wait to -1 so the initial
+ * interrupt doesn't put the task to sleep. */
+ tsk->thread.pfault_wait = -1;
}
+ put_task_struct(tsk);
} else {
/* signal bit not set -> a real page is missing. */
- get_task_struct(tsk);
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
- if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
+ if (tsk->thread.pfault_wait == -1) {
/* Completion interrupt was faster than the initial
- * interrupt (swapped in a -1 for pfault_wait). Set
- * pfault_wait back to zero and exit. This can be
- * done safely because tsk is running in kernel
- * mode and can't produce new pfaults. */
+ * interrupt (pfault_wait == -1). Set pfault_wait
+ * back to zero and exit. */
tsk->thread.pfault_wait = 0;
- set_task_state(tsk, TASK_RUNNING);
- put_task_struct(tsk);
- } else
+ } else {
+ /* Initial interrupt arrived before completion
+ * interrupt. Let the task sleep. */
+ tsk->thread.pfault_wait = 1;
+ list_add(&tsk->thread.list, &pfault_list);
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
set_tsk_need_resched(tsk);
+ }
+ }
+ spin_unlock(&pfault_lock);
+}
+
+static int __cpuinit pfault_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ struct thread_struct *thread, *next;
+ struct task_struct *tsk;
+
+ switch (action) {
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ spin_lock_irq(&pfault_lock);
+ list_for_each_entry_safe(thread, next, &pfault_list, list) {
+ thread->pfault_wait = 0;
+ list_del(&thread->list);
+ tsk = container_of(thread, struct task_struct, thread);
+ wake_up_process(tsk);
+ }
+ spin_unlock_irq(&pfault_lock);
+ break;
+ default:
+ break;
}
+ return NOTIFY_OK;
}
static int __init pfault_irq_init(void)
@@ -568,8 +607,10 @@ static int __init pfault_irq_init(void)
pfault_disable = 1;
return rc;
}
- if (pfault_init() == 0)
+ if (pfault_init() == 0) {
+ hotcpu_notifier(pfault_cpu_notify, 0);
return 0;
+ }
/* Tough luck, no pfault. */
pfault_disable = 1;