For some reason, this email did not make it to
[email protected], and therefore did not make it into
patchwork?
John?
-- Steve
On Wed, 26 Apr 2023 09:04:44 +0800
Tze-nan.Wu <[email protected]> wrote:
> From: "Tze-nan Wu" <[email protected]>
>
> In ring_buffer_reset_online_cpus, the buffer_size_kb write operation
> may permanently fail if the cpu_online_mask changes between two
> for_each_online_buffer_cpu loops. The number of increases and decreases
> on both cpu_buffer->resize_disabled and cpu_buffer->record_disabled may be
> inconsistent, causing some CPUs to have non-zero values for these atomic
> variables after the function returns.
>
> This issue can be reproduced by "echo 0 > trace" while hotplugging cpu.
> After reproducing success, we can find out buffer_size_kb will not be
> functional anymore.
>
> To prevent leaving 'resize_disabled' and 'record_disabled' non-zero after
> ring_buffer_reset_online_cpus returns, we ensure that each atomic variable
> has been set up before atomic_sub() to it.
>
> Cc: [email protected]
> Cc: [email protected]
> Fixes: b23d7a5f4a07 ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU")
> Reviewed-by: Cheng-Jui Wang <[email protected]>
> Signed-off-by: Tze-nan Wu <[email protected]>
> ---
> Changes from v4 to v5: https://lore.kernel.org/lkml/[email protected]/
> - Move the define before the function
> ---
> kernel/trace/ring_buffer.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 76a2d91eecad..253ef85a9ec3 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -5345,6 +5345,9 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
> }
> EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
>
> +/* Flag to ensure proper resetting of atomic variables */
> +#define RESET_BIT (1 << 30)
> +
> /**
> * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
> * @buffer: The ring buffer to reset a per cpu buffer of
> @@ -5361,20 +5364,27 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
> for_each_online_buffer_cpu(buffer, cpu) {
> cpu_buffer = buffer->buffers[cpu];
>
> - atomic_inc(&cpu_buffer->resize_disabled);
> + atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
> atomic_inc(&cpu_buffer->record_disabled);
> }
>
> /* Make sure all commits have finished */
> synchronize_rcu();
>
> - for_each_online_buffer_cpu(buffer, cpu) {
> + for_each_buffer_cpu(buffer, cpu) {
> cpu_buffer = buffer->buffers[cpu];
>
> + /*
> + * If a CPU came online during the synchronize_rcu(), then
> + * ignore it.
> + */
> + if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
> + continue;
> +
> reset_disabled_cpu_buffer(cpu_buffer);
>
> atomic_dec(&cpu_buffer->record_disabled);
> - atomic_dec(&cpu_buffer->resize_disabled);
> + atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
> }
>
> mutex_unlock(&buffer->mutex);
On Tue, 25 Apr 2023 21:17:37 -0400
Steven Rostedt <[email protected]> wrote:
> For some reason, this email did not make it to
> [email protected], and therefore did not make it into
> patchwork?
>
And the email was definitely Cc'd properly, as my reply made it to lore,
but not the original email.
https://lore.kernel.org/linux-trace-kernel/[email protected]/
-- Steve
Ran afoul of the taboo filters:
Illegal-Object: Syntax error in From: address found on vger.kernel.org:
From: Tze-nan.Wu<[email protected]>
^-missing end of mailbox
I've seen a few of these but I've been unable to replicate the problem.
I've a suspicion but so far been unable to prove the theory on what's wrong.
- John
On 4/25/23 18:17, Steven Rostedt wrote:
>
> For some reason, this email did not make it to
> [email protected], and therefore did not make it into
> patchwork?
>
> John?
>
> -- Steve
>
>
> On Wed, 26 Apr 2023 09:04:44 +0800
> Tze-nan.Wu <[email protected]> wrote:
>
>> From: "Tze-nan Wu" <[email protected]>
>>
>> In ring_buffer_reset_online_cpus, the buffer_size_kb write operation
>> may permanently fail if the cpu_online_mask changes between two
>> for_each_online_buffer_cpu loops. The number of increases and decreases
>> on both cpu_buffer->resize_disabled and cpu_buffer->record_disabled may be
>> inconsistent, causing some CPUs to have non-zero values for these atomic
>> variables after the function returns.
>>
>> This issue can be reproduced by "echo 0 > trace" while hotplugging cpu.
>> After reproducing success, we can find out buffer_size_kb will not be
>> functional anymore.
>>
>> To prevent leaving 'resize_disabled' and 'record_disabled' non-zero after
>> ring_buffer_reset_online_cpus returns, we ensure that each atomic variable
>> has been set up before atomic_sub() to it.
>>
>> Cc: [email protected]
>> Cc: [email protected]
>> Fixes: b23d7a5f4a07 ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU")
>> Reviewed-by: Cheng-Jui Wang <[email protected]>
>> Signed-off-by: Tze-nan Wu <[email protected]>
>> ---
>> Changes from v4 to v5: https://lore.kernel.org/lkml/[email protected]/
>> - Move the define before the function
>> ---
>> kernel/trace/ring_buffer.c | 16 +++++++++++++---
>> 1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
>> index 76a2d91eecad..253ef85a9ec3 100644
>> --- a/kernel/trace/ring_buffer.c
>> +++ b/kernel/trace/ring_buffer.c
>> @@ -5345,6 +5345,9 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
>> }
>> EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
>>
>> +/* Flag to ensure proper resetting of atomic variables */
>> +#define RESET_BIT (1 << 30)
>> +
>> /**
>> * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
>> * @buffer: The ring buffer to reset a per cpu buffer of
>> @@ -5361,20 +5364,27 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
>> for_each_online_buffer_cpu(buffer, cpu) {
>> cpu_buffer = buffer->buffers[cpu];
>>
>> - atomic_inc(&cpu_buffer->resize_disabled);
>> + atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
>> atomic_inc(&cpu_buffer->record_disabled);
>> }
>>
>> /* Make sure all commits have finished */
>> synchronize_rcu();
>>
>> - for_each_online_buffer_cpu(buffer, cpu) {
>> + for_each_buffer_cpu(buffer, cpu) {
>> cpu_buffer = buffer->buffers[cpu];
>>
>> + /*
>> + * If a CPU came online during the synchronize_rcu(), then
>> + * ignore it.
>> + */
>> + if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
>> + continue;
>> +
>> reset_disabled_cpu_buffer(cpu_buffer);
>>
>> atomic_dec(&cpu_buffer->record_disabled);
>> - atomic_dec(&cpu_buffer->resize_disabled);
>> + atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
>> }
>>
>> mutex_unlock(&buffer->mutex);
>
On Tue, 2023-04-25 at 19:58 -0700, John 'Warthog9' Hawley wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>
>
> Ran afoul of the taboo filters:
>
> Illegal-Object: Syntax error in From: address found on
> vger.kernel.org:
> From: Tze-nan.Wu<[email protected]>
> ^-missing end of mailbox
>
> I've seen a few of these but I've been unable to replicate the
> problem.
> I've a suspicion but so far been unable to prove the theory on what's
> wrong.
>
> - John
>
So I sent the patch again, but this time I changed the name field in
.gitconfig from "Tze-nan.Wu"(internal-use) to "Tze-nan Wu".
This can avoid the line "From: Tze-nan.Wu<[email protected]>"
being added to the mail when we execute "git send-email", and it works,
the last patch I sent is not filter out anymore.
---
Here is the magore difference between the patches:
old patch(fail):
From: "Tze-nan Wu" <[email protected]> <== (modify by editor
from Tze-nan.Wu to Tze-nan Wu)
---
new patch(success):
From: Tze-nan Wu <[email protected]>
---
- Tzenan
> On 4/25/23 18:17, Steven Rostedt wrote:
> >
> > For some reason, this email did not make it to
> > [email protected], and therefore did not make it
> > into
> > patchwork?
> >
> > John?
> >
> > -- Steve
> >
> >
> > On Wed, 26 Apr 2023 09:04:44 +0800
> > Tze-nan.Wu <[email protected]> wrote:
> >
> > > From: "Tze-nan Wu" <[email protected]>
> > >
> > > In ring_buffer_reset_online_cpus, the buffer_size_kb write
> > > operation
> > > may permanently fail if the cpu_online_mask changes between two
> > > for_each_online_buffer_cpu loops. The number of increases and
> > > decreases
> > > on both cpu_buffer->resize_disabled and cpu_buffer-
> > > >record_disabled may be
> > > inconsistent, causing some CPUs to have non-zero values for these
> > > atomic
> > > variables after the function returns.
> > >
> > > This issue can be reproduced by "echo 0 > trace" while
> > > hotplugging cpu.
> > > After reproducing success, we can find out buffer_size_kb will
> > > not be
> > > functional anymore.
> > >
> > > To prevent leaving 'resize_disabled' and 'record_disabled' non-
> > > zero after
> > > ring_buffer_reset_online_cpus returns, we ensure that each atomic
> > > variable
> > > has been set up before atomic_sub() to it.
> > >
> > > Cc: [email protected]
> > > Cc: [email protected]
> > > Fixes: b23d7a5f4a07 ("ring-buffer: speed up buffer resets by
> > > avoiding synchronize_rcu for each CPU")
> > > Reviewed-by: Cheng-Jui Wang <[email protected]>
> > > Signed-off-by: Tze-nan Wu <[email protected]>
> > > ---
> > > Changes from v4 to v5:
> > > https://lore.kernel.org/lkml/[email protected]/
> > > - Move the define before the function
> > > ---
> > > kernel/trace/ring_buffer.c | 16 +++++++++++++---
> > > 1 file changed, 13 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/kernel/trace/ring_buffer.c
> > > b/kernel/trace/ring_buffer.c
> > > index 76a2d91eecad..253ef85a9ec3 100644
> > > --- a/kernel/trace/ring_buffer.c
> > > +++ b/kernel/trace/ring_buffer.c
> > > @@ -5345,6 +5345,9 @@ void ring_buffer_reset_cpu(struct
> > > trace_buffer *buffer, int cpu)
> > > }
> > > EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
> > >
> > > +/* Flag to ensure proper resetting of atomic variables */
> > > +#define RESET_BIT (1 << 30)
> > > +
> > > /**
> > > * ring_buffer_reset_online_cpus - reset a ring buffer per CPU
> > > buffer
> > > * @buffer: The ring buffer to reset a per cpu buffer of
> > > @@ -5361,20 +5364,27 @@ void ring_buffer_reset_online_cpus(struct
> > > trace_buffer *buffer)
> > > for_each_online_buffer_cpu(buffer, cpu) {
> > > cpu_buffer = buffer->buffers[cpu];
> > >
> > > - atomic_inc(&cpu_buffer->resize_disabled);
> > > + atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
> > > atomic_inc(&cpu_buffer->record_disabled);
> > > }
> > >
> > > /* Make sure all commits have finished */
> > > synchronize_rcu();
> > >
> > > - for_each_online_buffer_cpu(buffer, cpu) {
> > > + for_each_buffer_cpu(buffer, cpu) {
> > > cpu_buffer = buffer->buffers[cpu];
> > >
> > > + /*
> > > + * If a CPU came online during the
> > > synchronize_rcu(), then
> > > + * ignore it.
> > > + */
> > > + if (!(atomic_read(&cpu_buffer->resize_disabled) &
> > > RESET_BIT))
> > > + continue;
> > > +
> > > reset_disabled_cpu_buffer(cpu_buffer);
> > >
> > > atomic_dec(&cpu_buffer->record_disabled);
> > > - atomic_dec(&cpu_buffer->resize_disabled);
> > > + atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
> > > }
> > >
> > > mutex_unlock(&buffer->mutex);