Merge branch 'parisc-3.15-4' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux

Pull parisc fixes from Helge Deller:
 "There are two patches in here:

  The first patch greatly improves latency and corrects the memory
  ordering in our light-weight atomic locking syscall.

  The second patch ratelimits printing of userspace segfaults in the
  same way as it's done on other platforms.  This fixes a possible DOS
  on parisc since it prevents the syslog to grow too fast.  For example,
  when the debian acl2 package was built on our debian buildd servers,
  this package produced lots of gigabytes in syslog in very short time
  and thus filled our harddisks, which then turned the server nearly
  completely unaccessible and unresponsive"

* 'parisc-3.15-4' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: Improve LWS-CAS performance
  parisc: ratelimit userspace segfault printing

4 files changed, 65 insertions, 46 deletions

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 1faefed32749..108d48e652af 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -22,6 +22,7 @@ config PARISC
         select GENERIC_SMP_IDLE_THREAD
         select GENERIC_STRNCPY_FROM_USER
         select SYSCTL_ARCH_UNALIGN_ALLOW
+        select SYSCTL_EXCEPTION_TRACE
         select HAVE_MOD_ARCH_SPECIFIC
         select VIRT_TO_BUS
         select MODULES_USE_ELF_RELA
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index a63bb179f79a..838786011037 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -589,10 +589,13 @@ cas_nocontend:
 # endif
 /* ENABLE_LWS_DEBUG */
 
+        rsm     PSW_SM_I, %r0                           /* Disable interrupts */
+        /* COW breaks can cause contention on UP systems */
         LDCW    0(%sr2,%r20), %r28                      /* Try to acquire the lock */
         cmpb,<>,n       %r0, %r28, cas_action           /* Did we get it? */
 cas_wouldblock:
         ldo     2(%r0), %r28                            /* 2nd case */
+        ssm     PSW_SM_I, %r0
         b       lws_exit                                /* Contended... */
         ldo     -EAGAIN(%r0), %r21                      /* Spin in userspace */
 
@@ -619,15 +622,17 @@ cas_action:
         stw     %r1, 4(%sr2,%r20)
 #endif
         /* The load and store could fail */
-1:      ldw     0(%sr3,%r26), %r28
+1:      ldw,ma  0(%sr3,%r26), %r28
         sub,<>  %r28, %r25, %r0
-2:      stw     %r24, 0(%sr3,%r26)
+2:      stw,ma  %r24, 0(%sr3,%r26)
         /* Free lock */
-        stw     %r20, 0(%sr2,%r20)
+        stw,ma  %r20, 0(%sr2,%r20)
 #if ENABLE_LWS_DEBUG
         /* Clear thread register indicator */
         stw     %r0, 4(%sr2,%r20)
 #endif
+        /* Enable interrupts */
+        ssm     PSW_SM_I, %r0
         /* Return to userspace, set no error */
         b       lws_exit
         copy    %r0, %r21
@@ -639,6 +644,7 @@ cas_action:
 #if ENABLE_LWS_DEBUG
         stw     %r0, 4(%sr2,%r20)
 #endif
+        ssm     PSW_SM_I, %r0
         b       lws_exit
         ldo     -EFAULT(%r0),%r21       /* set errno */
         nop
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 1cd1d0c83b6d..47ee620d15d2 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -25,6 +25,7 @@
 #include <linux/interrupt.h>
 #include <linux/console.h>
 #include <linux/bug.h>
+#include <linux/ratelimit.h>
 
 #include <asm/assembly.h>
 #include <asm/uaccess.h>
@@ -42,9 +43,6 @@
 
 #include "../math-emu/math-emu.h"       /* for handle_fpe() */
 
-#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */
-                          /*  dumped to the console via printk)          */
-
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 DEFINE_SPINLOCK(pa_dbit_lock);
 #endif
@@ -160,6 +158,17 @@ void show_regs(struct pt_regs *regs)
         }
 }
 
+static DEFINE_RATELIMIT_STATE(_hppa_rs,
+        DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
+
+#define parisc_printk_ratelimited(critical, regs, fmt, ...)     {             \
+        if ((critical || show_unhandled_signals) && __ratelimit(&_hppa_rs)) { \
+                printk(fmt, ##__VA_ARGS__);                                   \
+                show_regs(regs);                                              \
+        }                                                                     \
+}
+
+
 static void do_show_stack(struct unwind_frame_info *info)
 {
         int i = 1;
@@ -229,12 +238,10 @@ void die_if_kernel(char *str, struct pt_regs *regs, long err)
                 if (err == 0)
                         return; /* STFU */
 
-                printk(KERN_CRIT "%s (pid %d): %s (code %ld) at " RFMT "\n",
+                parisc_printk_ratelimited(1, regs,
+                        KERN_CRIT "%s (pid %d): %s (code %ld) at " RFMT "\n",
                         current->comm, task_pid_nr(current), str, err, regs->iaoq[0]);
-#ifdef PRINT_USER_FAULTS
-                /* XXX for debugging only */
-                show_regs(regs);
-#endif
+
                 return;
         }
 
@@ -321,14 +328,11 @@ static void handle_break(struct pt_regs *regs)
                         (tt == BUG_TRAP_TYPE_NONE) ? 9 : 0);
         }
 
-#ifdef PRINT_USER_FAULTS
-        if (unlikely(iir != GDB_BREAK_INSN)) {
-                printk(KERN_DEBUG "break %d,%d: pid=%d command='%s'\n",
+        if (unlikely(iir != GDB_BREAK_INSN))
+                parisc_printk_ratelimited(0, regs,
+                        KERN_DEBUG "break %d,%d: pid=%d command='%s'\n",
                         iir & 31, (iir>>13) & ((1<<13)-1),
                         task_pid_nr(current), current->comm);
-                show_regs(regs);
-        }
-#endif
 
         /* send standard GDB signal */
         handle_gdb_break(regs, TRAP_BRKPT);
@@ -758,11 +762,9 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
 
         default:
                 if (user_mode(regs)) {
-#ifdef PRINT_USER_FAULTS
-                        printk(KERN_DEBUG "\nhandle_interruption() pid=%d command='%s'\n",
-                            task_pid_nr(current), current->comm);
-                        show_regs(regs);
-#endif
+                        parisc_printk_ratelimited(0, regs, KERN_DEBUG
+                                "handle_interruption() pid=%d command='%s'\n",
+                                task_pid_nr(current), current->comm);
                         /* SIGBUS, for lack of a better one. */
                         si.si_signo = SIGBUS;
                         si.si_code = BUS_OBJERR;
@@ -779,16 +781,10 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
 
         if (user_mode(regs)) {
             if ((fault_space >> SPACEID_SHIFT) != (regs->sr[7] >> SPACEID_SHIFT)) {
-#ifdef PRINT_USER_FAULTS
-                if (fault_space == 0)
-                        printk(KERN_DEBUG "User Fault on Kernel Space ");
-                else
-                        printk(KERN_DEBUG "User Fault (long pointer) (fault %d) ",
-                               code);
-                printk(KERN_CONT "pid=%d command='%s'\n",
-                       task_pid_nr(current), current->comm);
-                show_regs(regs);
-#endif
+                parisc_printk_ratelimited(0, regs, KERN_DEBUG
+                                "User fault %d on space 0x%08lx, pid=%d command='%s'\n",
+                                code, fault_space,
+                                task_pid_nr(current), current->comm);
                 si.si_signo = SIGSEGV;
                 si.si_errno = 0;
                 si.si_code = SEGV_MAPERR;
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 747550762f3c..3ca9c1131cfe 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -19,10 +19,6 @@
 #include <asm/uaccess.h>
 #include <asm/traps.h>
 
-#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */
-                         /*  dumped to the console via printk)          */
-
-
 /* Various important other fields */
 #define bit22set(x)             (x & 0x00000200)
 #define bits23_25set(x)         (x & 0x000001c0)
@@ -34,6 +30,8 @@
 
 DEFINE_PER_CPU(struct exception_data, exception_data);
 
+int show_unhandled_signals = 1;
+
 /*
  * parisc_acctyp(unsigned int inst) --
  *    Given a PA-RISC memory access instruction, determine if the
@@ -173,6 +171,32 @@ int fixup_exception(struct pt_regs *regs)
         return 0;
 }
 
+/*
+ * Print out info about fatal segfaults, if the show_unhandled_signals
+ * sysctl is set:
+ */
+static inline void
+show_signal_msg(struct pt_regs *regs, unsigned long code,
+                unsigned long address, struct task_struct *tsk,
+                struct vm_area_struct *vma)
+{
+        if (!unhandled_signal(tsk, SIGSEGV))
+                return;
+
+        if (!printk_ratelimit())
+                return;
+
+        pr_warn("\n");
+        pr_warn("do_page_fault() command='%s' type=%lu address=0x%08lx",
+            tsk->comm, code, address);
+        print_vma_addr(KERN_CONT " in ", regs->iaoq[0]);
+        if (vma)
+                pr_warn(" vm_start = 0x%08lx, vm_end = 0x%08lx\n",
+                                vma->vm_start, vma->vm_end);
+
+        show_regs(regs);
+}
+
 void do_page_fault(struct pt_regs *regs, unsigned long code,
                               unsigned long address)
 {
@@ -270,16 +294,8 @@ bad_area:
         if (user_mode(regs)) {
                 struct siginfo si;
 
-#ifdef PRINT_USER_FAULTS
-                printk(KERN_DEBUG "\n");
-                printk(KERN_DEBUG "do_page_fault() pid=%d command='%s' type=%lu address=0x%08lx\n",
-                    task_pid_nr(tsk), tsk->comm, code, address);
-                if (vma) {
-                        printk(KERN_DEBUG "vm_start = 0x%08lx, vm_end = 0x%08lx\n",
-                                        vma->vm_start, vma->vm_end);
-                }
-                show_regs(regs);
-#endif
+                show_signal_msg(regs, code, address, tsk, vma);
+
                 switch (code) {
                 case 15:        /* Data TLB miss fault/Data page fault */
                         /* send SIGSEGV when outside of vma */