diff options
Diffstat (limited to 'arch/ia64/sn/kernel/sn2/sn2_smp.c')
| -rw-r--r-- | arch/ia64/sn/kernel/sn2/sn2_smp.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/arch/ia64/sn/kernel/sn2/sn2_smp.c b/arch/ia64/sn/kernel/sn2/sn2_smp.c index b2e1e746b47fc..d9d306c79f2d7 100644 --- a/arch/ia64/sn/kernel/sn2/sn2_smp.c +++ b/arch/ia64/sn/kernel/sn2/sn2_smp.c @@ -93,6 +93,27 @@ static inline unsigned long wait_piowc(void) return (ws & SH_PIO_WRITE_STATUS_WRITE_DEADLOCK_MASK) != 0; } +/** + * sn_migrate - SN-specific task migration actions + * @task: Task being migrated to new CPU + * + * SN2 PIO writes from separate CPUs are not guaranteed to arrive in order. + * Context switching user threads which have memory-mapped MMIO may cause + * PIOs to issue from seperate CPUs, thus the PIO writes must be drained + * from the previous CPU's Shub before execution resumes on the new CPU. + */ +void sn_migrate(struct task_struct *task) +{ + pda_t *last_pda = pdacpu(task_thread_info(task)->last_cpu); + volatile unsigned long *adr = last_pda->pio_write_status_addr; + unsigned long val = last_pda->pio_write_status_val; + + /* Drain PIO writes from old CPU's Shub */ + while (unlikely((*adr & SH_PIO_WRITE_STATUS_PENDING_WRITE_COUNT_MASK) + != val)) + cpu_relax(); +} + void sn_tlb_migrate_finish(struct mm_struct *mm) { /* flush_tlb_mm is inefficient if more than 1 users of mm */ |