2015-08-22 08:11:05

by Guenter Roeck

Subject: [PATCH -next] hrtimer: Fix hang seen if tick_init_highres() failed

Commit 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
drops the return code of hrtimer_switch_to_hres(). While doing so, it also
drops the return statement itself on failure. This may cause a system hang.
Seen when running arm:multi_v7_defconfig in qemu with devicetree file
vexpress-v2p-ca9.

Fixes: 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
Cc: Luiz Capitulino <[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>
---
kernel/time/hrtimer.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 5c4fe50e47d3..457a373e2181 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -695,6 +695,7 @@ static void hrtimer_switch_to_hres(void)
if (tick_init_highres()) {
printk(KERN_WARNING "Could not switch to high resolution "
"mode on CPU %d\n", base->cpu);
+ return;
}
base->hres_active = 1;
hrtimer_resolution = HIGH_RES_NSEC;
--
2.1.4

2015-08-22 09:01:09

by tip-bot for Vasyl Gomonovych

Subject: [tip:timers/core] hrtimer: Handle failure of tick_init_highres() gracefully

Commit-ID: 85e1cd6e769dfc84995270d0a4838021fcb8602d
Gitweb: http://git.kernel.org/tip/85e1cd6e769dfc84995270d0a4838021fcb8602d
Author: Guenter Roeck <[email protected]>
AuthorDate: Sat, 22 Aug 2015 01:10:47 -0700
Committer: Thomas Gleixner <[email protected]>
CommitDate: Sat, 22 Aug 2015 10:57:50 +0200

hrtimer: Handle failure of tick_init_highres() gracefully

Commit 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
drops the return code of hrtimer_switch_to_hres(). While doing so, it also
drops the return statement itself on failure. This may cause a system hang.
Seen when running arm:multi_v7_defconfig in qemu with devicetree file
vexpress-v2p-ca9.

Fixes: 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
Cc: Luiz Capitulino <[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
---
kernel/time/hrtimer.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 5c4fe50..457a373 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -695,6 +695,7 @@ static void hrtimer_switch_to_hres(void)
if (tick_init_highres()) {
printk(KERN_WARNING "Could not switch to high resolution "
"mode on CPU %d\n", base->cpu);
+ return;
}
base->hres_active = 1;
hrtimer_resolution = HIGH_RES_NSEC;

2015-08-22 21:25:52

by Luiz Capitulino

Subject: Re: [PATCH -next] hrtimer: Fix hang seen if tick_init_highres() failed

On Sat, 22 Aug 2015 01:10:47 -0700
Guenter Roeck <[email protected]> wrote:

> Commit 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
> drops the return code of hrtimer_switch_to_hres(). While doing so, it also
> drops the return statement itself on failure. This may cause a system hang.
> Seen when running arm:multi_v7_defconfig in qemu with devicetree file
> vexpress-v2p-ca9.
>
> Fixes: 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
> Cc: Luiz Capitulino <[email protected]>
> Signed-off-by: Guenter Roeck <[email protected]>

Thanks for catching it Guenter!

Reviewed-by: Luiz Capitulino <[email protected]>

> ---
> kernel/time/hrtimer.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
> index 5c4fe50e47d3..457a373e2181 100644
> --- a/kernel/time/hrtimer.c
> +++ b/kernel/time/hrtimer.c
> @@ -695,6 +695,7 @@ static void hrtimer_switch_to_hres(void)
> if (tick_init_highres()) {
> printk(KERN_WARNING "Could not switch to high resolution "
> "mode on CPU %d\n", base->cpu);
> + return;
> }
> base->hres_active = 1;
> hrtimer_resolution = HIGH_RES_NSEC;