* [PATCH] sched/vtime: Prevent unstable evaluation of WARN(vtime->state)
@ 2020-01-23 18:08 Frederic Weisbecker
2020-02-14 16:23 ` Frederic Weisbecker
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Frederic Weisbecker @ 2020-01-23 18:08 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra; +Cc: LKML, Chris Wilson, Frederic Weisbecker
From: Chris Wilson <chris@chris-wilson.co.uk>
As the vtime is sampled under loose seqcount protection by kcpustat, the
vtime fields may change as the code flows. Where logic dictates a field
has a static value, use a READ_ONCE.
Fixes: 74722bb223d0 ("sched/vtime: Bring up complete kcpustat accessor")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
kernel/sched/cputime.c | 41 ++++++++++++++++++++++-------------------
1 file changed, 22 insertions(+), 19 deletions(-)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index d43318a489f2..df3577149d2e 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -912,8 +912,10 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
} while (read_seqcount_retry(&vtime->seqcount, seq));
}
-static int vtime_state_check(struct vtime *vtime, int cpu)
+static int vtime_state_fetch(struct vtime *vtime, int cpu)
{
+ int state = READ_ONCE(vtime->state);
+
/*
* We raced against a context switch, fetch the
* kcpustat task again.
@@ -930,10 +932,10 @@ static int vtime_state_check(struct vtime *vtime, int cpu)
*
* Case 1) is ok but 2) is not. So wait for a safe VTIME state.
*/
- if (vtime->state == VTIME_INACTIVE)
+ if (state == VTIME_INACTIVE)
return -EAGAIN;
- return 0;
+ return state;
}
static u64 kcpustat_user_vtime(struct vtime *vtime)
@@ -952,14 +954,15 @@ static int kcpustat_field_vtime(u64 *cpustat,
{
struct vtime *vtime = &tsk->vtime;
unsigned int seq;
- int err;
do {
+ int state;
+
seq = read_seqcount_begin(&vtime->seqcount);
- err = vtime_state_check(vtime, cpu);
- if (err < 0)
- return err;
+ state = vtime_state_fetch(vtime, cpu);
+ if (state < 0)
+ return state;
*val = cpustat[usage];
@@ -972,7 +975,7 @@ static int kcpustat_field_vtime(u64 *cpustat,
*/
switch (usage) {
case CPUTIME_SYSTEM:
- if (vtime->state == VTIME_SYS)
+ if (state == VTIME_SYS)
*val += vtime->stime + vtime_delta(vtime);
break;
case CPUTIME_USER:
@@ -984,11 +987,11 @@ static int kcpustat_field_vtime(u64 *cpustat,
*val += kcpustat_user_vtime(vtime);
break;
case CPUTIME_GUEST:
- if (vtime->state == VTIME_GUEST && task_nice(tsk) <= 0)
+ if (state == VTIME_GUEST && task_nice(tsk) <= 0)
*val += vtime->gtime + vtime_delta(vtime);
break;
case CPUTIME_GUEST_NICE:
- if (vtime->state == VTIME_GUEST && task_nice(tsk) > 0)
+ if (state == VTIME_GUEST && task_nice(tsk) > 0)
*val += vtime->gtime + vtime_delta(vtime);
break;
default:
@@ -1039,23 +1042,23 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
{
struct vtime *vtime = &tsk->vtime;
unsigned int seq;
- int err;
do {
u64 *cpustat;
u64 delta;
+ int state;
seq = read_seqcount_begin(&vtime->seqcount);
- err = vtime_state_check(vtime, cpu);
- if (err < 0)
- return err;
+ state = vtime_state_fetch(vtime, cpu);
+ if (state < 0)
+ return state;
*dst = *src;
cpustat = dst->cpustat;
/* Task is sleeping, dead or idle, nothing to add */
- if (vtime->state < VTIME_SYS)
+ if (state < VTIME_SYS)
continue;
delta = vtime_delta(vtime);
@@ -1064,15 +1067,15 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
* Task runs either in user (including guest) or kernel space,
* add pending nohz time to the right place.
*/
- if (vtime->state == VTIME_SYS) {
+ if (state == VTIME_SYS) {
cpustat[CPUTIME_SYSTEM] += vtime->stime + delta;
- } else if (vtime->state == VTIME_USER) {
+ } else if (state == VTIME_USER) {
if (task_nice(tsk) > 0)
cpustat[CPUTIME_NICE] += vtime->utime + delta;
else
cpustat[CPUTIME_USER] += vtime->utime + delta;
} else {
- WARN_ON_ONCE(vtime->state != VTIME_GUEST);
+ WARN_ON_ONCE(state != VTIME_GUEST);
if (task_nice(tsk) > 0) {
cpustat[CPUTIME_GUEST_NICE] += vtime->gtime + delta;
cpustat[CPUTIME_NICE] += vtime->gtime + delta;
@@ -1083,7 +1086,7 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
}
} while (read_seqcount_retry(&vtime->seqcount, seq));
- return err;
+ return 0;
}
void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu)
--
2.25.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] sched/vtime: Prevent unstable evaluation of WARN(vtime->state)
2020-01-23 18:08 [PATCH] sched/vtime: Prevent unstable evaluation of WARN(vtime->state) Frederic Weisbecker
@ 2020-02-14 16:23 ` Frederic Weisbecker
2020-02-27 13:34 ` Frederic Weisbecker
2020-03-06 14:42 ` [tip: sched/core] " tip-bot2 for Chris Wilson
2 siblings, 0 replies; 4+ messages in thread
From: Frederic Weisbecker @ 2020-02-14 16:23 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra; +Cc: LKML, Chris Wilson
On Thu, Jan 23, 2020 at 07:08:49PM +0100, Frederic Weisbecker wrote:
> From: Chris Wilson <chris@chris-wilson.co.uk>
>
> As the vtime is sampled under loose seqcount protection by kcpustat, the
> vtime fields may change as the code flows. Where logic dictates a field
> has a static value, use a READ_ONCE.
>
> Fixes: 74722bb223d0 ("sched/vtime: Bring up complete kcpustat accessor")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Ping?
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] sched/vtime: Prevent unstable evaluation of WARN(vtime->state)
2020-01-23 18:08 [PATCH] sched/vtime: Prevent unstable evaluation of WARN(vtime->state) Frederic Weisbecker
2020-02-14 16:23 ` Frederic Weisbecker
@ 2020-02-27 13:34 ` Frederic Weisbecker
2020-03-06 14:42 ` [tip: sched/core] " tip-bot2 for Chris Wilson
2 siblings, 0 replies; 4+ messages in thread
From: Frederic Weisbecker @ 2020-02-27 13:34 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra; +Cc: LKML, Chris Wilson
Ping (again)?
On Thu, Jan 23, 2020 at 07:08:49PM +0100, Frederic Weisbecker wrote:
> From: Chris Wilson <chris@chris-wilson.co.uk>
>
> As the vtime is sampled under loose seqcount protection by kcpustat, the
> vtime fields may change as the code flows. Where logic dictates a field
> has a static value, use a READ_ONCE.
>
> Fixes: 74722bb223d0 ("sched/vtime: Bring up complete kcpustat accessor")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> ---
> kernel/sched/cputime.c | 41 ++++++++++++++++++++++-------------------
> 1 file changed, 22 insertions(+), 19 deletions(-)
>
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> index d43318a489f2..df3577149d2e 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -912,8 +912,10 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
> } while (read_seqcount_retry(&vtime->seqcount, seq));
> }
>
> -static int vtime_state_check(struct vtime *vtime, int cpu)
> +static int vtime_state_fetch(struct vtime *vtime, int cpu)
> {
> + int state = READ_ONCE(vtime->state);
> +
> /*
> * We raced against a context switch, fetch the
> * kcpustat task again.
> @@ -930,10 +932,10 @@ static int vtime_state_check(struct vtime *vtime, int cpu)
> *
> * Case 1) is ok but 2) is not. So wait for a safe VTIME state.
> */
> - if (vtime->state == VTIME_INACTIVE)
> + if (state == VTIME_INACTIVE)
> return -EAGAIN;
>
> - return 0;
> + return state;
> }
>
> static u64 kcpustat_user_vtime(struct vtime *vtime)
> @@ -952,14 +954,15 @@ static int kcpustat_field_vtime(u64 *cpustat,
> {
> struct vtime *vtime = &tsk->vtime;
> unsigned int seq;
> - int err;
>
> do {
> + int state;
> +
> seq = read_seqcount_begin(&vtime->seqcount);
>
> - err = vtime_state_check(vtime, cpu);
> - if (err < 0)
> - return err;
> + state = vtime_state_fetch(vtime, cpu);
> + if (state < 0)
> + return state;
>
> *val = cpustat[usage];
>
> @@ -972,7 +975,7 @@ static int kcpustat_field_vtime(u64 *cpustat,
> */
> switch (usage) {
> case CPUTIME_SYSTEM:
> - if (vtime->state == VTIME_SYS)
> + if (state == VTIME_SYS)
> *val += vtime->stime + vtime_delta(vtime);
> break;
> case CPUTIME_USER:
> @@ -984,11 +987,11 @@ static int kcpustat_field_vtime(u64 *cpustat,
> *val += kcpustat_user_vtime(vtime);
> break;
> case CPUTIME_GUEST:
> - if (vtime->state == VTIME_GUEST && task_nice(tsk) <= 0)
> + if (state == VTIME_GUEST && task_nice(tsk) <= 0)
> *val += vtime->gtime + vtime_delta(vtime);
> break;
> case CPUTIME_GUEST_NICE:
> - if (vtime->state == VTIME_GUEST && task_nice(tsk) > 0)
> + if (state == VTIME_GUEST && task_nice(tsk) > 0)
> *val += vtime->gtime + vtime_delta(vtime);
> break;
> default:
> @@ -1039,23 +1042,23 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
> {
> struct vtime *vtime = &tsk->vtime;
> unsigned int seq;
> - int err;
>
> do {
> u64 *cpustat;
> u64 delta;
> + int state;
>
> seq = read_seqcount_begin(&vtime->seqcount);
>
> - err = vtime_state_check(vtime, cpu);
> - if (err < 0)
> - return err;
> + state = vtime_state_fetch(vtime, cpu);
> + if (state < 0)
> + return state;
>
> *dst = *src;
> cpustat = dst->cpustat;
>
> /* Task is sleeping, dead or idle, nothing to add */
> - if (vtime->state < VTIME_SYS)
> + if (state < VTIME_SYS)
> continue;
>
> delta = vtime_delta(vtime);
> @@ -1064,15 +1067,15 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
> * Task runs either in user (including guest) or kernel space,
> * add pending nohz time to the right place.
> */
> - if (vtime->state == VTIME_SYS) {
> + if (state == VTIME_SYS) {
> cpustat[CPUTIME_SYSTEM] += vtime->stime + delta;
> - } else if (vtime->state == VTIME_USER) {
> + } else if (state == VTIME_USER) {
> if (task_nice(tsk) > 0)
> cpustat[CPUTIME_NICE] += vtime->utime + delta;
> else
> cpustat[CPUTIME_USER] += vtime->utime + delta;
> } else {
> - WARN_ON_ONCE(vtime->state != VTIME_GUEST);
> + WARN_ON_ONCE(state != VTIME_GUEST);
> if (task_nice(tsk) > 0) {
> cpustat[CPUTIME_GUEST_NICE] += vtime->gtime + delta;
> cpustat[CPUTIME_NICE] += vtime->gtime + delta;
> @@ -1083,7 +1086,7 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
> }
> } while (read_seqcount_retry(&vtime->seqcount, seq));
>
> - return err;
> + return 0;
> }
>
> void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu)
> --
> 2.25.0
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip: sched/core] sched/vtime: Prevent unstable evaluation of WARN(vtime->state)
2020-01-23 18:08 [PATCH] sched/vtime: Prevent unstable evaluation of WARN(vtime->state) Frederic Weisbecker
2020-02-14 16:23 ` Frederic Weisbecker
2020-02-27 13:34 ` Frederic Weisbecker
@ 2020-03-06 14:42 ` tip-bot2 for Chris Wilson
2 siblings, 0 replies; 4+ messages in thread
From: tip-bot2 for Chris Wilson @ 2020-03-06 14:42 UTC (permalink / raw)
To: linux-tip-commits
Cc: Chris Wilson, Frederic Weisbecker, Peter Zijlstra (Intel),
Ingo Molnar, x86, LKML
The following commit has been merged into the sched/core branch of tip:
Commit-ID: f1dfdab694eb3838ac26f4b73695929c07d92a33
Gitweb: https://git.kernel.org/tip/f1dfdab694eb3838ac26f4b73695929c07d92a33
Author: Chris Wilson <chris@chris-wilson.co.uk>
AuthorDate: Thu, 23 Jan 2020 19:08:49 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 06 Mar 2020 12:57:16 +01:00
sched/vtime: Prevent unstable evaluation of WARN(vtime->state)
As the vtime is sampled under loose seqcount protection by kcpustat, the
vtime fields may change as the code flows. Where logic dictates a field
has a static value, use a READ_ONCE.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 74722bb223d0 ("sched/vtime: Bring up complete kcpustat accessor")
Link: https://lkml.kernel.org/r/20200123180849.28486-1-frederic@kernel.org
---
kernel/sched/cputime.c | 41 ++++++++++++++++++++++-------------------
1 file changed, 22 insertions(+), 19 deletions(-)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index cff3e65..dac9104 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -909,8 +909,10 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
} while (read_seqcount_retry(&vtime->seqcount, seq));
}
-static int vtime_state_check(struct vtime *vtime, int cpu)
+static int vtime_state_fetch(struct vtime *vtime, int cpu)
{
+ int state = READ_ONCE(vtime->state);
+
/*
* We raced against a context switch, fetch the
* kcpustat task again.
@@ -927,10 +929,10 @@ static int vtime_state_check(struct vtime *vtime, int cpu)
*
* Case 1) is ok but 2) is not. So wait for a safe VTIME state.
*/
- if (vtime->state == VTIME_INACTIVE)
+ if (state == VTIME_INACTIVE)
return -EAGAIN;
- return 0;
+ return state;
}
static u64 kcpustat_user_vtime(struct vtime *vtime)
@@ -949,14 +951,15 @@ static int kcpustat_field_vtime(u64 *cpustat,
{
struct vtime *vtime = &tsk->vtime;
unsigned int seq;
- int err;
do {
+ int state;
+
seq = read_seqcount_begin(&vtime->seqcount);
- err = vtime_state_check(vtime, cpu);
- if (err < 0)
- return err;
+ state = vtime_state_fetch(vtime, cpu);
+ if (state < 0)
+ return state;
*val = cpustat[usage];
@@ -969,7 +972,7 @@ static int kcpustat_field_vtime(u64 *cpustat,
*/
switch (usage) {
case CPUTIME_SYSTEM:
- if (vtime->state == VTIME_SYS)
+ if (state == VTIME_SYS)
*val += vtime->stime + vtime_delta(vtime);
break;
case CPUTIME_USER:
@@ -981,11 +984,11 @@ static int kcpustat_field_vtime(u64 *cpustat,
*val += kcpustat_user_vtime(vtime);
break;
case CPUTIME_GUEST:
- if (vtime->state == VTIME_GUEST && task_nice(tsk) <= 0)
+ if (state == VTIME_GUEST && task_nice(tsk) <= 0)
*val += vtime->gtime + vtime_delta(vtime);
break;
case CPUTIME_GUEST_NICE:
- if (vtime->state == VTIME_GUEST && task_nice(tsk) > 0)
+ if (state == VTIME_GUEST && task_nice(tsk) > 0)
*val += vtime->gtime + vtime_delta(vtime);
break;
default:
@@ -1036,23 +1039,23 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
{
struct vtime *vtime = &tsk->vtime;
unsigned int seq;
- int err;
do {
u64 *cpustat;
u64 delta;
+ int state;
seq = read_seqcount_begin(&vtime->seqcount);
- err = vtime_state_check(vtime, cpu);
- if (err < 0)
- return err;
+ state = vtime_state_fetch(vtime, cpu);
+ if (state < 0)
+ return state;
*dst = *src;
cpustat = dst->cpustat;
/* Task is sleeping, dead or idle, nothing to add */
- if (vtime->state < VTIME_SYS)
+ if (state < VTIME_SYS)
continue;
delta = vtime_delta(vtime);
@@ -1061,15 +1064,15 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
* Task runs either in user (including guest) or kernel space,
* add pending nohz time to the right place.
*/
- if (vtime->state == VTIME_SYS) {
+ if (state == VTIME_SYS) {
cpustat[CPUTIME_SYSTEM] += vtime->stime + delta;
- } else if (vtime->state == VTIME_USER) {
+ } else if (state == VTIME_USER) {
if (task_nice(tsk) > 0)
cpustat[CPUTIME_NICE] += vtime->utime + delta;
else
cpustat[CPUTIME_USER] += vtime->utime + delta;
} else {
- WARN_ON_ONCE(vtime->state != VTIME_GUEST);
+ WARN_ON_ONCE(state != VTIME_GUEST);
if (task_nice(tsk) > 0) {
cpustat[CPUTIME_GUEST_NICE] += vtime->gtime + delta;
cpustat[CPUTIME_NICE] += vtime->gtime + delta;
@@ -1080,7 +1083,7 @@ static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst,
}
} while (read_seqcount_retry(&vtime->seqcount, seq));
- return err;
+ return 0;
}
void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu)
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-03-06 14:42 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-01-23 18:08 [PATCH] sched/vtime: Prevent unstable evaluation of WARN(vtime->state) Frederic Weisbecker
2020-02-14 16:23 ` Frederic Weisbecker
2020-02-27 13:34 ` Frederic Weisbecker
2020-03-06 14:42 ` [tip: sched/core] " tip-bot2 for Chris Wilson
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).