s390/mcck: cleanup user process termination path

If a machine check interrupt hits while user process is
running __s390_handle_mcck() helper function is called
directly from the interrupt handler and terminates the
current process by calling make_task_dead() routine.

The make_task_dead() is not allowed to be called from
interrupt context which forces the machine check handler
switch to the kernel stack and enable local interrupts
first.

The __s390_handle_mcck() could also be called to service
pending work, but this time from the external interrupts
handler. It is the machine check handler that establishes
the work and schedules the external interrupt, therefore
the machine check interrupt itself should be disabled
while reading out the corresponding variable:

	local_mcck_disable();
	mcck = *this_cpu_ptr(&cpu_mcck);
	memset(this_cpu_ptr(&cpu_mcck), 0, sizeof(mcck));
	local_mcck_enable();

However, local_mcck_disable() does not have effect when
__s390_handle_mcck() is called directly form the machine
check handler, since the machine check interrupt is still
disabled. Therefore, it is not the opening bracket to the
following local_mcck_enable() function.

Simplify the user process termination flow by scheduling
the external interrupt and killing the affected process
from the interrupt context.

Assume a kernel-generated signal is always delivered and
ignore a value returned by do_send_sig_info() funciton.

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/arch/s390/include/asm/nmi.h b/arch/s390/include/asm/nmi.h
index af1cd3a6f4060666aee6373891b40ff4e3ece46b..227466ce9e4163cf733fac65df2677c6c6dcb53e 100644 (file)
--- a/arch/s390/include/asm/nmi.h
+++ b/arch/s390/include/asm/nmi.h
@@ -101,9 +101,8 @@ void nmi_alloc_mcesa_early(u64 *mcesad);
 int nmi_alloc_mcesa(u64 *mcesad);
 void nmi_free_mcesa(u64 *mcesad);
 
-void s390_handle_mcck(struct pt_regs *regs);
-void __s390_handle_mcck(void);
-int s390_do_machine_check(struct pt_regs *regs);
+void s390_handle_mcck(void);
+void s390_do_machine_check(struct pt_regs *regs);
 
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_S390_NMI_H */

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index c8d8c996093674f9ffd7a2f6cf11ffa8717d6705..76a06f3d367116ad196675455aef001b7140d060 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -562,16 +562,6 @@ ENTRY(mcck_int_handler)
        xc      __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
        lgr     %r2,%r11                # pass pointer to pt_regs
        brasl   %r14,s390_do_machine_check
-       cghi    %r2,0
-       je      .Lmcck_return
-       lg      %r1,__LC_KERNEL_STACK   # switch to kernel stack
-       mvc     STACK_FRAME_OVERHEAD(__PT_SIZE,%r1),0(%r11)
-       xc      __SF_BACKCHAIN(8,%r1),__SF_BACKCHAIN(%r1)
-       la      %r11,STACK_FRAME_OVERHEAD(%r1)
-       lgr     %r2,%r11
-       lgr     %r15,%r1
-       brasl   %r14,s390_handle_mcck
-.Lmcck_return:
        lctlg   %c1,%c1,__PT_CR1(%r11)
        lmg     %r0,%r10,__PT_R0(%r11)
        mvc     __LC_RETURN_MCCK_PSW(16),__PT_PSW(%r11) # move return PSW

diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 56d9c559afa1f8ab0b3a98185b28542b912dbffe..38ec0487521c42e8aed1895b3e9dc22d85fe6379 100644 (file)
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -156,7 +156,7 @@ NOKPROBE_SYMBOL(s390_handle_damage);
  * Main machine check handler function. Will be called with interrupts disabled
  * and machine checks enabled.
  */
-void __s390_handle_mcck(void)
+void s390_handle_mcck(void)
 {
        struct mcck_struct mcck;
 
@@ -192,23 +192,16 @@ void __s390_handle_mcck(void)
        if (mcck.stp_queue)
                stp_queue_work();
        if (mcck.kill_task) {
-               local_irq_enable();
                printk(KERN_EMERG "mcck: Terminating task because of machine "
                       "malfunction (code 0x%016lx).\n", mcck.mcck_code);
                printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
                       current->comm, current->pid);
-               make_task_dead(SIGSEGV);
+               if (is_global_init(current))
+                       panic("mcck: Attempting to kill init!\n");
+               do_send_sig_info(SIGKILL, SEND_SIG_PRIV, current, PIDTYPE_PID);
        }
 }
 
-void noinstr s390_handle_mcck(struct pt_regs *regs)
-{
-       trace_hardirqs_off();
-       pai_kernel_enter(regs);
-       __s390_handle_mcck();
-       pai_kernel_exit(regs);
-       trace_hardirqs_on();
-}
 /*
  * returns 0 if register contents could be validated
  * returns 1 otherwise
@@ -373,7 +366,7 @@ NOKPROBE_SYMBOL(s390_backup_mcck_info);
 /*
  * machine check handler.
  */
-int notrace s390_do_machine_check(struct pt_regs *regs)
+void notrace s390_do_machine_check(struct pt_regs *regs)
 {
        static int ipd_count;
        static DEFINE_SPINLOCK(ipd_lock);
@@ -503,16 +496,10 @@ int notrace s390_do_machine_check(struct pt_regs *regs)
        }
        clear_cpu_flag(CIF_MCCK_GUEST);
 
-       if (user_mode(regs) && mcck_pending) {
-               irqentry_nmi_exit(regs, irq_state);
-               return 1;
-       }
-
        if (mcck_pending)
                schedule_mcck_handler();
 
        irqentry_nmi_exit(regs, irq_state);
-       return 0;
 }
 NOKPROBE_SYMBOL(s390_do_machine_check);
 

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 23c427284773c1323928eb6cc89f735152d1eb69..97961522b317a7b3448e51877badb5c880f49eb0 100644 (file)
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -522,7 +522,7 @@ static void smp_handle_ext_call(void)
        if (test_bit(ec_call_function_single, &bits))
                generic_smp_call_function_single_interrupt();
        if (test_bit(ec_mcck_pending, &bits))
-               __s390_handle_mcck();
+               s390_handle_mcck();
        if (test_bit(ec_irq_work, &bits))
                irq_work_run();
 }