Re: [PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
On Fri, Aug 7, 2015 at 7:03 PM, Nathan Lynch wrote:
> Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the
> real timekeeper last") it has become possible on arm64 to:
>
> - Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
> via syscall.
> - Subsequently obtain a timestamp for the same clock ID via VDSO which
> predates the first timestamp (by one jiffy).
>
> This is because arm64's update_vsyscall is deriving the coarse time
> using the __current_kernel_time interface, when it should really be
> using the timekeeper object provided to it by the timekeeping core.
> It happened to work before only because __current_kernel_time would
> access the same timekeeper object which had been passed to
> update_vsyscall. This is no longer the case.
>
> Signed-off-by: Nathan Lynch
> ---
> arch/arm64/kernel/vdso.c | 7 +++
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
> index ec37ab3f524f..97bc68f4c689 100644
> --- a/arch/arm64/kernel/vdso.c
> +++ b/arch/arm64/kernel/vdso.c
> @@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm
> *bprm,
> */
> void update_vsyscall(struct timekeeper *tk)
> {
> - struct timespec xtime_coarse;
> u32 use_syscall = strcmp(tk->tkr_mono.clock->name,
> "arch_sys_counter");
>
> ++vdso_data->tb_seq_count;
> smp_wmb();
>
> - xtime_coarse = __current_kernel_time();
> vdso_data->use_syscall = use_syscall;
> - vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec;
> - vdso_data->xtime_coarse_nsec= xtime_coarse.tv_nsec;
> + vdso_data->xtime_coarse_sec = tk->xtime_sec;
> + vdso_data->xtime_coarse_nsec= tk->tkr_mono.xtime_nsec >>
> + tk->tkr_mono.shift;
> vdso_data->wtm_clock_sec=
> tk->wall_to_monotonic.tv_sec;
> vdso_data->wtm_clock_nsec =
> tk->wall_to_monotonic.tv_nsec;
>
(Sorry for the slow response, I've been out on vacation).
If its worth anything now:
Acked-by: John Stultz
thanks
-john
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Re: [PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
On Fri, Aug 7, 2015 at 7:03 PM, Nathan Lynch nathan_ly...@mentor.com wrote:
Since 906c55579a63 (timekeeping: Copy the shadow-timekeeper over the
real timekeeper last) it has become possible on arm64 to:
- Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
via syscall.
- Subsequently obtain a timestamp for the same clock ID via VDSO which
predates the first timestamp (by one jiffy).
This is because arm64's update_vsyscall is deriving the coarse time
using the __current_kernel_time interface, when it should really be
using the timekeeper object provided to it by the timekeeping core.
It happened to work before only because __current_kernel_time would
access the same timekeeper object which had been passed to
update_vsyscall. This is no longer the case.
Signed-off-by: Nathan Lynch nathan_ly...@mentor.com
---
arch/arm64/kernel/vdso.c | 7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index ec37ab3f524f..97bc68f4c689 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm
*bprm,
*/
void update_vsyscall(struct timekeeper *tk)
{
- struct timespec xtime_coarse;
u32 use_syscall = strcmp(tk-tkr_mono.clock-name,
arch_sys_counter);
++vdso_data-tb_seq_count;
smp_wmb();
- xtime_coarse = __current_kernel_time();
vdso_data-use_syscall = use_syscall;
- vdso_data-xtime_coarse_sec = xtime_coarse.tv_sec;
- vdso_data-xtime_coarse_nsec= xtime_coarse.tv_nsec;
+ vdso_data-xtime_coarse_sec = tk-xtime_sec;
+ vdso_data-xtime_coarse_nsec= tk-tkr_mono.xtime_nsec
+ tk-tkr_mono.shift;
vdso_data-wtm_clock_sec=
tk-wall_to_monotonic.tv_sec;
vdso_data-wtm_clock_nsec =
tk-wall_to_monotonic.tv_nsec;
(Sorry for the slow response, I've been out on vacation).
If its worth anything now:
Acked-by: John Stultz john.stu...@linaro.org
thanks
-john
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Re: [PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
On Mon, Aug 10, 2015 at 10:22:53AM +0100, Will Deacon wrote:
> On Sat, Aug 08, 2015 at 03:03:23AM +0100, Nathan Lynch wrote:
> > Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the
> > real timekeeper last") it has become possible on arm64 to:
> >
> > - Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
> > via syscall.
> > - Subsequently obtain a timestamp for the same clock ID via VDSO which
> > predates the first timestamp (by one jiffy).
> >
> > This is because arm64's update_vsyscall is deriving the coarse time
> > using the __current_kernel_time interface, when it should really be
> > using the timekeeper object provided to it by the timekeeping core.
> > It happened to work before only because __current_kernel_time would
> > access the same timekeeper object which had been passed to
> > update_vsyscall. This is no longer the case.
> >
> > Signed-off-by: Nathan Lynch
> > ---
> > arch/arm64/kernel/vdso.c | 7 +++
> > 1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
> > index ec37ab3f524f..97bc68f4c689 100644
> > --- a/arch/arm64/kernel/vdso.c
> > +++ b/arch/arm64/kernel/vdso.c
> > @@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm
> > *bprm,
> > */
> > void update_vsyscall(struct timekeeper *tk)
> > {
> > - struct timespec xtime_coarse;
> > u32 use_syscall = strcmp(tk->tkr_mono.clock->name, "arch_sys_counter");
> >
> > ++vdso_data->tb_seq_count;
> > smp_wmb();
> >
> > - xtime_coarse = __current_kernel_time();
> > vdso_data->use_syscall = use_syscall;
> > - vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec;
> > - vdso_data->xtime_coarse_nsec= xtime_coarse.tv_nsec;
> > + vdso_data->xtime_coarse_sec = tk->xtime_sec;
> > + vdso_data->xtime_coarse_nsec= tk->tkr_mono.xtime_nsec >>
> > + tk->tkr_mono.shift;
> > vdso_data->wtm_clock_sec= tk->wall_to_monotonic.tv_sec;
> > vdso_data->wtm_clock_nsec = tk->wall_to_monotonic.tv_nsec;
>
> Looks good,
>
> Acked-by: Will Deacon
>
> There's probably still time for Catalin to pick this up for 4.2.
Applied, I'll send a pull request today/tomorrow. Thanks.
--
Catalin
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Re: [PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
Hi Nathan,
On Sat, Aug 08, 2015 at 03:03:23AM +0100, Nathan Lynch wrote:
> Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the
> real timekeeper last") it has become possible on arm64 to:
>
> - Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
> via syscall.
> - Subsequently obtain a timestamp for the same clock ID via VDSO which
> predates the first timestamp (by one jiffy).
>
> This is because arm64's update_vsyscall is deriving the coarse time
> using the __current_kernel_time interface, when it should really be
> using the timekeeper object provided to it by the timekeeping core.
> It happened to work before only because __current_kernel_time would
> access the same timekeeper object which had been passed to
> update_vsyscall. This is no longer the case.
>
> Signed-off-by: Nathan Lynch
> ---
> arch/arm64/kernel/vdso.c | 7 +++
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
> index ec37ab3f524f..97bc68f4c689 100644
> --- a/arch/arm64/kernel/vdso.c
> +++ b/arch/arm64/kernel/vdso.c
> @@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm
> *bprm,
> */
> void update_vsyscall(struct timekeeper *tk)
> {
> - struct timespec xtime_coarse;
> u32 use_syscall = strcmp(tk->tkr_mono.clock->name, "arch_sys_counter");
>
> ++vdso_data->tb_seq_count;
> smp_wmb();
>
> - xtime_coarse = __current_kernel_time();
> vdso_data->use_syscall = use_syscall;
> - vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec;
> - vdso_data->xtime_coarse_nsec= xtime_coarse.tv_nsec;
> + vdso_data->xtime_coarse_sec = tk->xtime_sec;
> + vdso_data->xtime_coarse_nsec= tk->tkr_mono.xtime_nsec >>
> + tk->tkr_mono.shift;
> vdso_data->wtm_clock_sec= tk->wall_to_monotonic.tv_sec;
> vdso_data->wtm_clock_nsec = tk->wall_to_monotonic.tv_nsec;
Looks good,
Acked-by: Will Deacon
There's probably still time for Catalin to pick this up for 4.2.
Will
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To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
On Mon, Aug 10, 2015 at 10:22:53AM +0100, Will Deacon wrote:
On Sat, Aug 08, 2015 at 03:03:23AM +0100, Nathan Lynch wrote:
Since 906c55579a63 (timekeeping: Copy the shadow-timekeeper over the
real timekeeper last) it has become possible on arm64 to:
- Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
via syscall.
- Subsequently obtain a timestamp for the same clock ID via VDSO which
predates the first timestamp (by one jiffy).
This is because arm64's update_vsyscall is deriving the coarse time
using the __current_kernel_time interface, when it should really be
using the timekeeper object provided to it by the timekeeping core.
It happened to work before only because __current_kernel_time would
access the same timekeeper object which had been passed to
update_vsyscall. This is no longer the case.
Signed-off-by: Nathan Lynch nathan_ly...@mentor.com
---
arch/arm64/kernel/vdso.c | 7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index ec37ab3f524f..97bc68f4c689 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm
*bprm,
*/
void update_vsyscall(struct timekeeper *tk)
{
- struct timespec xtime_coarse;
u32 use_syscall = strcmp(tk-tkr_mono.clock-name, arch_sys_counter);
++vdso_data-tb_seq_count;
smp_wmb();
- xtime_coarse = __current_kernel_time();
vdso_data-use_syscall = use_syscall;
- vdso_data-xtime_coarse_sec = xtime_coarse.tv_sec;
- vdso_data-xtime_coarse_nsec= xtime_coarse.tv_nsec;
+ vdso_data-xtime_coarse_sec = tk-xtime_sec;
+ vdso_data-xtime_coarse_nsec= tk-tkr_mono.xtime_nsec
+ tk-tkr_mono.shift;
vdso_data-wtm_clock_sec= tk-wall_to_monotonic.tv_sec;
vdso_data-wtm_clock_nsec = tk-wall_to_monotonic.tv_nsec;
Looks good,
Acked-by: Will Deacon will.dea...@arm.com
There's probably still time for Catalin to pick this up for 4.2.
Applied, I'll send a pull request today/tomorrow. Thanks.
--
Catalin
--
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the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
Hi Nathan,
On Sat, Aug 08, 2015 at 03:03:23AM +0100, Nathan Lynch wrote:
Since 906c55579a63 (timekeeping: Copy the shadow-timekeeper over the
real timekeeper last) it has become possible on arm64 to:
- Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
via syscall.
- Subsequently obtain a timestamp for the same clock ID via VDSO which
predates the first timestamp (by one jiffy).
This is because arm64's update_vsyscall is deriving the coarse time
using the __current_kernel_time interface, when it should really be
using the timekeeper object provided to it by the timekeeping core.
It happened to work before only because __current_kernel_time would
access the same timekeeper object which had been passed to
update_vsyscall. This is no longer the case.
Signed-off-by: Nathan Lynch nathan_ly...@mentor.com
---
arch/arm64/kernel/vdso.c | 7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index ec37ab3f524f..97bc68f4c689 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm
*bprm,
*/
void update_vsyscall(struct timekeeper *tk)
{
- struct timespec xtime_coarse;
u32 use_syscall = strcmp(tk-tkr_mono.clock-name, arch_sys_counter);
++vdso_data-tb_seq_count;
smp_wmb();
- xtime_coarse = __current_kernel_time();
vdso_data-use_syscall = use_syscall;
- vdso_data-xtime_coarse_sec = xtime_coarse.tv_sec;
- vdso_data-xtime_coarse_nsec= xtime_coarse.tv_nsec;
+ vdso_data-xtime_coarse_sec = tk-xtime_sec;
+ vdso_data-xtime_coarse_nsec= tk-tkr_mono.xtime_nsec
+ tk-tkr_mono.shift;
vdso_data-wtm_clock_sec= tk-wall_to_monotonic.tv_sec;
vdso_data-wtm_clock_nsec = tk-wall_to_monotonic.tv_nsec;
Looks good,
Acked-by: Will Deacon will.dea...@arm.com
There's probably still time for Catalin to pick this up for 4.2.
Will
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the
real timekeeper last") it has become possible on arm64 to:
- Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
via syscall.
- Subsequently obtain a timestamp for the same clock ID via VDSO which
predates the first timestamp (by one jiffy).
This is because arm64's update_vsyscall is deriving the coarse time
using the __current_kernel_time interface, when it should really be
using the timekeeper object provided to it by the timekeeping core.
It happened to work before only because __current_kernel_time would
access the same timekeeper object which had been passed to
update_vsyscall. This is no longer the case.
Signed-off-by: Nathan Lynch
---
arch/arm64/kernel/vdso.c | 7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index ec37ab3f524f..97bc68f4c689 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
*/
void update_vsyscall(struct timekeeper *tk)
{
- struct timespec xtime_coarse;
u32 use_syscall = strcmp(tk->tkr_mono.clock->name, "arch_sys_counter");
++vdso_data->tb_seq_count;
smp_wmb();
- xtime_coarse = __current_kernel_time();
vdso_data->use_syscall = use_syscall;
- vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec;
- vdso_data->xtime_coarse_nsec= xtime_coarse.tv_nsec;
+ vdso_data->xtime_coarse_sec = tk->xtime_sec;
+ vdso_data->xtime_coarse_nsec= tk->tkr_mono.xtime_nsec >>
+ tk->tkr_mono.shift;
vdso_data->wtm_clock_sec= tk->wall_to_monotonic.tv_sec;
vdso_data->wtm_clock_nsec = tk->wall_to_monotonic.tv_nsec;
--
2.1.0
--
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Please read the FAQ at http://www.tux.org/lkml/
[PATCH 2/2] arm64: VDSO: fix coarse clock monotonicity regression
Since 906c55579a63 (timekeeping: Copy the shadow-timekeeper over the
real timekeeper last) it has become possible on arm64 to:
- Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
via syscall.
- Subsequently obtain a timestamp for the same clock ID via VDSO which
predates the first timestamp (by one jiffy).
This is because arm64's update_vsyscall is deriving the coarse time
using the __current_kernel_time interface, when it should really be
using the timekeeper object provided to it by the timekeeping core.
It happened to work before only because __current_kernel_time would
access the same timekeeper object which had been passed to
update_vsyscall. This is no longer the case.
Signed-off-by: Nathan Lynch nathan_ly...@mentor.com
---
arch/arm64/kernel/vdso.c | 7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index ec37ab3f524f..97bc68f4c689 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -199,16 +199,15 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
*/
void update_vsyscall(struct timekeeper *tk)
{
- struct timespec xtime_coarse;
u32 use_syscall = strcmp(tk-tkr_mono.clock-name, arch_sys_counter);
++vdso_data-tb_seq_count;
smp_wmb();
- xtime_coarse = __current_kernel_time();
vdso_data-use_syscall = use_syscall;
- vdso_data-xtime_coarse_sec = xtime_coarse.tv_sec;
- vdso_data-xtime_coarse_nsec= xtime_coarse.tv_nsec;
+ vdso_data-xtime_coarse_sec = tk-xtime_sec;
+ vdso_data-xtime_coarse_nsec= tk-tkr_mono.xtime_nsec
+ tk-tkr_mono.shift;
vdso_data-wtm_clock_sec= tk-wall_to_monotonic.tv_sec;
vdso_data-wtm_clock_nsec = tk-wall_to_monotonic.tv_nsec;
--
2.1.0
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