powerpc/pseries: Protect against hogging the cpu while setting up the stats

[linux-2.6-block.git] / arch / powerpc / platforms / pseries / lpar.c

diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index ec5a7893f71b54d2935063718445c5710cbab76c..ae7040f5956425de4dba5bc02640f9f59147e97d 100644 (file)
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -75,7 +75,7 @@ static u8 dtl_mask = DTL_LOG_PREEMPT;
 static u8 dtl_mask;
 #endif
 
-void alloc_dtl_buffers(void)
+void alloc_dtl_buffers(unsigned long *time_limit)
 {
        int cpu;
        struct paca_struct *pp;
@@ -99,6 +99,11 @@ void alloc_dtl_buffers(void)
                pp->dispatch_log = dtl;
                pp->dispatch_log_end = dtl + N_DISPATCH_LOG;
                pp->dtl_curr = dtl;
+
+               if (time_limit && time_after(jiffies, *time_limit)) {
+                       cond_resched();
+                       *time_limit = jiffies + HZ;
+               }
        }
 }
 
@@ -168,7 +173,7 @@ static int vcpudispatch_stats_freq = 50;
 static __be32 *vcpu_associativity, *pcpu_associativity;
 
 
-static void free_dtl_buffers(void)
+static void free_dtl_buffers(unsigned long *time_limit)
 {
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
        int cpu;
@@ -183,6 +188,11 @@ static void free_dtl_buffers(void)
                pp->dispatch_log = 0;
                pp->dispatch_log_end = 0;
                pp->dtl_curr = 0;
+
+               if (time_limit && time_after(jiffies, *time_limit)) {
+                       cond_resched();
+                       *time_limit = jiffies + HZ;
+               }
        }
 #endif
 }
@@ -442,7 +452,7 @@ static void reset_global_dtl_mask(void)
                lppaca_of(cpu).dtl_enable_mask = dtl_mask;
 }
 
-static int dtl_worker_enable(void)
+static int dtl_worker_enable(unsigned long *time_limit)
 {
        int rc = 0, state;
 
@@ -454,13 +464,13 @@ static int dtl_worker_enable(void)
        set_global_dtl_mask(DTL_LOG_ALL);
 
        /* Setup dtl buffers and register those */
-       alloc_dtl_buffers();
+       alloc_dtl_buffers(time_limit);
 
        state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/dtl:online",
                                        dtl_worker_online, dtl_worker_offline);
        if (state < 0) {
                pr_err("vcpudispatch_stats: unable to setup workqueue for DTL processing\n");
-               free_dtl_buffers();
+               free_dtl_buffers(time_limit);
                reset_global_dtl_mask();
                write_unlock(&dtl_access_lock);
                rc = -EINVAL;
@@ -472,10 +482,10 @@ out:
        return rc;
 }
 
-static void dtl_worker_disable(void)
+static void dtl_worker_disable(unsigned long *time_limit)
 {
        cpuhp_remove_state(dtl_worker_state);
-       free_dtl_buffers();
+       free_dtl_buffers(time_limit);
        reset_global_dtl_mask();
        write_unlock(&dtl_access_lock);
 }
@@ -483,6 +493,7 @@ static void dtl_worker_disable(void)
 static ssize_t vcpudispatch_stats_write(struct file *file, const char __user *p,
                size_t count, loff_t *ppos)
 {
+       unsigned long time_limit = jiffies + HZ;
        struct vcpu_dispatch_data *disp;
        int rc, cmd, cpu;
        char buf[16];
@@ -517,13 +528,13 @@ static ssize_t vcpudispatch_stats_write(struct file *file, const char __user *p,
                        disp->last_disp_cpu = -1;
                }
 
-               rc = dtl_worker_enable();
+               rc = dtl_worker_enable(&time_limit);
                if (rc) {
                        destroy_cpu_associativity();
                        goto out;
                }
        } else {
-               dtl_worker_disable();
+               dtl_worker_disable(&time_limit);
                destroy_cpu_associativity();
        }