[PATCH][2.6.7-mm4] perfctr update 5/6: reduce stack usage
From: Mikael Pettersson (mikpe_at_csd.uu.se)
Date: 06/30/04
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Date: Wed, 30 Jun 2004 14:21:52 +0200 (MEST) To: akpm@osdl.org
- Reduce stack usage by using kmalloc() instead of the stack
for temporary state and control copies.
- Eliminate some unnecessary cpumask_t copies. Use newish
cpus_intersects() instead of cpus_and(); !cpus_empty().
Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>
--- linux-2.6.7-mm4/drivers/perfctr/init.c.~1~ 2004-06-29 19:01:56.000000000 +0200
+++ linux-2.6.7-mm4/drivers/perfctr/init.c 2004-06-30 01:14:20.000000000 +0200
@@ -54,14 +54,12 @@
if (infop && copy_to_user(infop, &perfctr_info, sizeof perfctr_info))
return -EFAULT;
if (cpusp) {
- cpumask_t cpus = cpu_online_map;
- int err = cpus_copy_to_user(cpusp, &cpus);
+ int err = cpus_copy_to_user(cpusp, &cpu_online_map);
if (err)
return err;
}
if (forbiddenp) {
- cpumask_t cpus = perfctr_cpus_forbidden_mask;
- int err = cpus_copy_to_user(forbiddenp, &cpus);
+ int err = cpus_copy_to_user(forbiddenp, &perfctr_cpus_forbidden_mask);
if (err)
return err;
}
--- linux-2.6.7-mm4/drivers/perfctr/virtual.c.~1~ 2004-06-29 19:11:30.000000000 +0200
+++ linux-2.6.7-mm4/drivers/perfctr/virtual.c 2004-06-30 02:29:12.000000000 +0200
@@ -364,10 +364,7 @@
struct vperfctr *perfctr,
cpumask_t new_mask)
{
- cpumask_t tmp;
-
- cpus_and(tmp, new_mask, perfctr_cpus_forbidden_mask);
- if (!cpus_empty(tmp)) {
+ if (cpus_intersects(new_mask, perfctr_cpus_forbidden_mask)) {
atomic_set(&perfctr->bad_cpus_allowed, 1);
printk(KERN_WARNING "perfctr: process %d (comm %s) issued unsafe"
" set_cpus_allowed() on process %d (comm %s)\n",
@@ -391,7 +388,7 @@
const struct vperfctr_control __user *argp,
struct task_struct *tsk)
{
- struct vperfctr_control control;
+ struct vperfctr_control *control;
int err;
unsigned int next_cstatus;
unsigned int nrctrs, i;
@@ -399,18 +396,29 @@
if (!tsk)
return -ESRCH; /* attempt to update unlinked perfctr */
- if (copy_from_user(&control, argp, sizeof control))
- return -EFAULT;
+ /* The control object can be large (over 300 bytes on i386),
+ so kmalloc() it instead of storing it on the stack.
+ We must use task-private storage to prevent racing with a
+ monitor process attaching to us before the non-preemptible
+ perfctr update step. Therefore we cannot store the copy
+ in the perfctr object itself. */
+ control = kmalloc(sizeof(*control), GFP_USER);
+ if (!control)
+ return -ENOMEM;
+
+ err = -EFAULT;
+ if (copy_from_user(control, argp, sizeof *control))
+ goto out_kfree;
- if (control.cpu_control.nractrs || control.cpu_control.nrictrs) {
- cpumask_t tmp, old_mask, new_mask;
+ if (control->cpu_control.nractrs || control->cpu_control.nrictrs) {
+ cpumask_t old_mask, new_mask;
- tmp = perfctr_cpus_forbidden_mask;
old_mask = tsk->cpus_allowed;
- cpus_andnot(new_mask, old_mask, tmp);
+ cpus_andnot(new_mask, old_mask, perfctr_cpus_forbidden_mask);
+ err = -EINVAL;
if (cpus_empty(new_mask))
- return -EINVAL;
+ goto out_kfree;
if (!cpus_equal(new_mask, old_mask))
set_cpus_allowed(tsk, new_mask);
}
@@ -424,7 +432,7 @@
perfctr->cpu_state.cstatus = 0;
vperfctr_clear_iresume_cstatus(perfctr);
}
- perfctr->cpu_state.control = control.cpu_control;
+ perfctr->cpu_state.control = control->cpu_control;
/* remote access note: perfctr_cpu_update_control() is ok */
err = perfctr_cpu_update_control(&perfctr->cpu_state, 0);
if (err < 0)
@@ -434,14 +442,14 @@
goto out;
/* XXX: validate si_signo? */
- perfctr->si_signo = control.si_signo;
+ perfctr->si_signo = control->si_signo;
if (!perfctr_cstatus_has_tsc(next_cstatus))
perfctr->cpu_state.tsc_sum = 0;
nrctrs = perfctr_cstatus_nrctrs(next_cstatus);
for(i = 0; i < nrctrs; ++i)
- if (!(control.preserve & (1<<i)))
+ if (!(control->preserve & (1<<i)))
perfctr->cpu_state.pmc[i].sum = 0;
if (tsk == current)
@@ -449,6 +457,8 @@
out:
preempt_enable();
+ out_kfree:
+ kfree(control);
return err;
}
@@ -500,8 +510,21 @@
struct vperfctr_control __user *controlp,
const struct task_struct *tsk)
{
- struct perfctr_sum_ctrs sum;
- struct vperfctr_control control;
+ struct {
+ struct perfctr_sum_ctrs sum;
+ struct vperfctr_control control;
+ } *tmp;
+ int ret;
+
+ /* The state snapshot can be large (almost 500 bytes on i386),
+ so kmalloc() it instead of storing it on the stack.
+ We must use task-private storage to prevent racing with a
+ monitor process attaching to us during the preemptible
+ copy_to_user() step. Therefore we cannot store the snapshot
+ in the perfctr object itself. */
+ tmp = kmalloc(sizeof(*tmp), GFP_USER);
+ if (!tmp)
+ return -ENOMEM;
/* PREEMPT note: While we're reading our own control, another
process may ptrace ATTACH to us and update our control.
@@ -515,22 +538,26 @@
}
if (sump) { //sum = perfctr->cpu_state.sum;
int j;
- sum.tsc = perfctr->cpu_state.tsc_sum;
- for(j = 0; j < ARRAY_SIZE(sum.pmc); ++j)
- sum.pmc[j] = perfctr->cpu_state.pmc[j].sum;
+ tmp->sum.tsc = perfctr->cpu_state.tsc_sum;
+ for(j = 0; j < ARRAY_SIZE(tmp->sum.pmc); ++j)
+ tmp->sum.pmc[j] = perfctr->cpu_state.pmc[j].sum;
}
if (controlp) {
- control.si_signo = perfctr->si_signo;
- control.cpu_control = perfctr->cpu_state.control;
- control.preserve = 0;
+ tmp->control.si_signo = perfctr->si_signo;
+ tmp->control.cpu_control = perfctr->cpu_state.control;
+ tmp->control.preserve = 0;
}
if (tsk == current)
preempt_enable();
- if (sump && copy_to_user(sump, &sum, sizeof sum))
- return -EFAULT;
- if (controlp && copy_to_user(controlp, &control, sizeof control))
- return -EFAULT;
- return 0;
+ ret = -EFAULT;
+ if (sump && copy_to_user(sump, &tmp->sum, sizeof tmp->sum))
+ goto out;
+ if (controlp && copy_to_user(controlp, &tmp->control, sizeof tmp->control))
+ goto out;
+ ret = 0;
+ out:
+ kfree(tmp);
+ return ret;
}
/****************************************************************
-
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