s390/etr,stp: fix possible deadlock on machine check
The first level machine check handler for etr and stp machine checks may
call queue_work() while in nmi context. This may deadlock e.g. if the
machine check happened when the interrupted context did hold a lock, that
also will be acquired by queue_work().
Therefore split etr and stp machine check handling into first and second
level handling. The second level handling will then issue the queue_work()
call in process context which avoids the potential deadlock.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/etr.h b/arch/s390/include/asm/etr.h
index f7e5c36..105f90e 100644
--- a/arch/s390/include/asm/etr.h
+++ b/arch/s390/include/asm/etr.h
@@ -211,8 +211,9 @@
#define ETR_PTFF_SGS 0x43 /* set gross steering rate */
/* Functions needed by the machine check handler */
-void etr_switch_to_local(void);
-void etr_sync_check(void);
+int etr_switch_to_local(void);
+int etr_sync_check(void);
+void etr_queue_work(void);
/* notifier for syncs */
extern struct atomic_notifier_head s390_epoch_delta_notifier;
@@ -253,7 +254,8 @@
} __attribute__ ((packed));
/* Functions needed by the machine check handler */
-void stp_sync_check(void);
-void stp_island_check(void);
+int stp_sync_check(void);
+int stp_island_check(void);
+void stp_queue_work(void);
#endif /* __S390_ETR_H */
diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 0ae6f8e..4082885 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -28,6 +28,8 @@
int kill_task;
int channel_report;
int warning;
+ unsigned int etr_queue : 1;
+ unsigned int stp_queue : 1;
unsigned long long mcck_code;
};
@@ -81,6 +83,10 @@
if (xchg(&mchchk_wng_posted, 1) == 0)
kill_cad_pid(SIGPWR, 1);
}
+ if (mcck.etr_queue)
+ etr_queue_work();
+ if (mcck.stp_queue)
+ stp_queue_work();
if (mcck.kill_task) {
local_irq_enable();
printk(KERN_EMERG "mcck: Terminating task because of machine "
@@ -323,13 +329,15 @@
if (mci->ed && mci->ec) {
/* External damage */
if (S390_lowcore.external_damage_code & (1U << ED_ETR_SYNC))
- etr_sync_check();
+ mcck->etr_queue |= etr_sync_check();
if (S390_lowcore.external_damage_code & (1U << ED_ETR_SWITCH))
- etr_switch_to_local();
+ mcck->etr_queue |= etr_switch_to_local();
if (S390_lowcore.external_damage_code & (1U << ED_STP_SYNC))
- stp_sync_check();
+ mcck->stp_queue |= stp_sync_check();
if (S390_lowcore.external_damage_code & (1U << ED_STP_ISLAND))
- stp_island_check();
+ mcck->stp_queue |= stp_island_check();
+ if (mcck->etr_queue || mcck->stp_queue)
+ set_cpu_flag(CIF_MCCK_PENDING);
}
if (mci->se)
/* Storage error uncorrected */
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 017c3a9..99f84ac31 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -542,16 +542,17 @@
* Switch to local machine check. This is called when the last usable
* ETR port goes inactive. After switch to local the clock is not in sync.
*/
-void etr_switch_to_local(void)
+int etr_switch_to_local(void)
{
if (!etr_eacr.sl)
- return;
+ return 0;
disable_sync_clock(NULL);
if (!test_and_set_bit(ETR_EVENT_SWITCH_LOCAL, &etr_events)) {
etr_eacr.es = etr_eacr.sl = 0;
etr_setr(&etr_eacr);
- queue_work(time_sync_wq, &etr_work);
+ return 1;
}
+ return 0;
}
/*
@@ -560,16 +561,22 @@
* After a ETR sync check the clock is not in sync. The machine check
* is broadcasted to all cpus at the same time.
*/
-void etr_sync_check(void)
+int etr_sync_check(void)
{
if (!etr_eacr.es)
- return;
+ return 0;
disable_sync_clock(NULL);
if (!test_and_set_bit(ETR_EVENT_SYNC_CHECK, &etr_events)) {
etr_eacr.es = 0;
etr_setr(&etr_eacr);
- queue_work(time_sync_wq, &etr_work);
+ return 1;
}
+ return 0;
+}
+
+void etr_queue_work(void)
+{
+ queue_work(time_sync_wq, &etr_work);
}
/*
@@ -1504,10 +1511,10 @@
* After a STP sync check the clock is not in sync. The machine check
* is broadcasted to all cpus at the same time.
*/
-void stp_sync_check(void)
+int stp_sync_check(void)
{
disable_sync_clock(NULL);
- queue_work(time_sync_wq, &stp_work);
+ return 1;
}
/*
@@ -1516,12 +1523,16 @@
* have matching CTN ids and have a valid stratum-1 configuration
* but the configurations do not match.
*/
-void stp_island_check(void)
+int stp_island_check(void)
{
disable_sync_clock(NULL);
- queue_work(time_sync_wq, &stp_work);
+ return 1;
}
+void stp_queue_work(void)
+{
+ queue_work(time_sync_wq, &stp_work);
+}
static int stp_sync_clock(void *data)
{