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s390/etr,stp: fix possible deadlock on machine check

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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>
This commit is contained in:
Heiko Carstens 2015-10-09 13:48:03 +02:00 committed by Martin Schwidefsky
parent 7cc8944e13
commit 29b0a8250b
3 changed files with 39 additions and 18 deletions
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10
arch/s390/include/asm/etr.h
View File

@ -211,8 +211,9 @@ static inline int etr_ptff(void *ptff_block, unsigned int func)
#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 @@ struct stp_sstpi {
} __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 */

16
arch/s390/kernel/nmi.c
View File

@ -28,6 +28,8 @@ struct mcck_struct {
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 @@ void s390_handle_mcck(void)
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 @@ void notrace s390_do_machine_check(struct pt_regs *regs)
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 */

31
arch/s390/kernel/time.c
View File

@ -542,16 +542,17 @@ arch_initcall(etr_init);
* 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 @@ void etr_switch_to_local(void)
* 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 @@ static void stp_timing_alert(struct stp_irq_parm *intparm)
* 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 @@ void stp_sync_check(void)
* 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)
{