Merge to Fedora kernel-2.6.18-1.2224_FC5 patched with stable patch-2.6.18.1-vs2.0...

[linux-2.6.git] / kernel / posix-cpu-timers.c

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 13c0be2..0779b48 100644 (file)
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -6,7 +6,6 @@
 #include <linux/posix-timers.h>
 #include <asm/uaccess.h>
 #include <linux/errno.h>
-#include <linux/vs_cvirt.h>
 
 static int check_clock(const clockid_t which_clock)
 {
@@ -88,6 +87,19 @@ static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
        return a;
 }
 
+/*
+ * Divide and limit the result to res >= 1
+ *
+ * This is necessary to prevent signal delivery starvation, when the result of
+ * the division would be rounded down to 0.
+ */
+static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
+{
+       cputime_t res = cputime_div(time, div);
+
+       return max_t(cputime_t, res, 1);
+}
+
 /*
  * Update expiry time from increment, and increase overrun count,
  * given the current clock sample.
@@ -484,8 +496,8 @@ static void process_timer_rebalance(struct task_struct *p,
                BUG();
                break;
        case CPUCLOCK_PROF:
-               left = cputime_div(cputime_sub(expires.cpu, val.cpu),
-                                  nthreads);
+               left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
+                                      nthreads);
                do {
                        if (likely(!(t->flags & PF_EXITING))) {
                                ticks = cputime_add(prof_ticks(t), left);
@@ -499,8 +511,8 @@ static void process_timer_rebalance(struct task_struct *p,
                } while (t != p);
                break;
        case CPUCLOCK_VIRT:
-               left = cputime_div(cputime_sub(expires.cpu, val.cpu),
-                                  nthreads);
+               left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
+                                      nthreads);
                do {
                        if (likely(!(t->flags & PF_EXITING))) {
                                ticks = cputime_add(virt_ticks(t), left);
@@ -516,6 +528,7 @@ static void process_timer_rebalance(struct task_struct *p,
        case CPUCLOCK_SCHED:
                nsleft = expires.sched - val.sched;
                do_div(nsleft, nthreads);
+               nsleft = max_t(unsigned long long, nsleft, 1);
                do {
                        if (likely(!(t->flags & PF_EXITING))) {
                                ns = t->sched_time + nsleft;
@@ -1160,12 +1173,13 @@ static void check_process_timers(struct task_struct *tsk,
 
                prof_left = cputime_sub(prof_expires, utime);
                prof_left = cputime_sub(prof_left, stime);
-               prof_left = cputime_div(prof_left, nthreads);
+               prof_left = cputime_div_non_zero(prof_left, nthreads);
                virt_left = cputime_sub(virt_expires, utime);
-               virt_left = cputime_div(virt_left, nthreads);
+               virt_left = cputime_div_non_zero(virt_left, nthreads);
                if (sched_expires) {
                        sched_left = sched_expires - sched_time;
                        do_div(sched_left, nthreads);
+                       sched_left = max_t(unsigned long long, sched_left, 1);
                } else {
                        sched_left = 0;
                }