[PATCH] doc/eal: add signal safety warning

[PATCH] doc/eal: add signal safety warning

[Stephen Hemminger]

The DPDK is not designed to be used from a signal handler.
Add a notice in the documentation describing this limitation,
similar to Linux signal-safety manual page.

Bugzilla ID: 1030
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 doc/guides/prog_guide/env_abstraction_layer.rst | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
index 5f0748fba1c0..36ab4b5ba9b6 100644
--- a/doc/guides/prog_guide/env_abstraction_layer.rst
+++ b/doc/guides/prog_guide/env_abstraction_layer.rst
@@ -732,6 +732,19 @@ controlled with tools like taskset (Linux) or cpuset (FreeBSD),
 - with affinity restricted to 2-3, the Control Threads will end up on
   CPU 2 (main lcore, which is the default when no CPU is available).
 
+Signal Safety
+~~~~~~~~~~~~~
+
+The DPDK functions in general can not be safely called from a signal handler.
+Most functions are not async-signal-safe because they can acquire locks
+and other resources that make them nonrentrant.
+
+To avoid problems with unsafe functions, can be avoided if required
+signals are blocked and a mechanism such as signalfd (Linux) is used
+to convert the asynchronous signals into messages that are processed
+by a EAL thread.
+
+
 .. _known_issue_label:
 
 Known Issues
-- 
2.35.1

Re: [PATCH] doc/eal: add signal safety warning

[Tyler Retzlaff]

On Fri, Jun 10, 2022 at 08:23:43AM -0700, Stephen Hemminger wrote:
> The DPDK is not designed to be used from a signal handler.
> Add a notice in the documentation describing this limitation,
> similar to Linux signal-safety manual page.
> 
> Bugzilla ID: 1030
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>  doc/guides/prog_guide/env_abstraction_layer.rst | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> index 5f0748fba1c0..36ab4b5ba9b6 100644
> --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> @@ -732,6 +732,19 @@ controlled with tools like taskset (Linux) or cpuset (FreeBSD),
>  - with affinity restricted to 2-3, the Control Threads will end up on
>    CPU 2 (main lcore, which is the default when no CPU is available).
>  
> +Signal Safety
> +~~~~~~~~~~~~~
> +
> +The DPDK functions in general can not be safely called from a signal handler.
> +Most functions are not async-signal-safe because they can acquire locks
> +and other resources that make them nonrentrant.
> +
> +To avoid problems with unsafe functions, can be avoided if required
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^

above doesn't quite read right for me, maybe a missing word / needs
re-wording?

> +signals are blocked and a mechanism such as signalfd (Linux) is used
> +to convert the asynchronous signals into messages that are processed
> +by a EAL thread.
> +
> +
>  .. _known_issue_label:
>  
>  Known Issues
> -- 
> 2.35.1

Re: [PATCH] doc/eal: add signal safety warning

[Stephen Hemminger]

On Fri, 10 Jun 2022 15:53:34 -0700
Tyler Retzlaff <roretzla@linux.microsoft.com> wrote:

> On Fri, Jun 10, 2022 at 08:23:43AM -0700, Stephen Hemminger wrote:
> > The DPDK is not designed to be used from a signal handler.
> > Add a notice in the documentation describing this limitation,
> > similar to Linux signal-safety manual page.
> > 
> > Bugzilla ID: 1030
> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > ---
> >  doc/guides/prog_guide/env_abstraction_layer.rst | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> > index 5f0748fba1c0..36ab4b5ba9b6 100644
> > --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> > +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> > @@ -732,6 +732,19 @@ controlled with tools like taskset (Linux) or cpuset (FreeBSD),
> >  - with affinity restricted to 2-3, the Control Threads will end up on
> >    CPU 2 (main lcore, which is the default when no CPU is available).
> >  
> > +Signal Safety
> > +~~~~~~~~~~~~~
> > +
> > +The DPDK functions in general can not be safely called from a signal handler.
> > +Most functions are not async-signal-safe because they can acquire locks
> > +and other resources that make them nonrentrant.
> > +
> > +To avoid problems with unsafe functions, can be avoided if required
>                                  ^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> above doesn't quite read right for me, maybe a missing word / needs
> re-wording?

Yes, will reword that

Re: [PATCH] doc/eal: add signal safety warning

[Tyler Retzlaff]

On Fri, Jun 10, 2022 at 08:23:43AM -0700, Stephen Hemminger wrote:
> The DPDK is not designed to be used from a signal handler.
> Add a notice in the documentation describing this limitation,
> similar to Linux signal-safety manual page.
> 
> Bugzilla ID: 1030
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>

> ---
>  doc/guides/prog_guide/env_abstraction_layer.rst | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> index 5f0748fba1c0..36ab4b5ba9b6 100644
> --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> @@ -732,6 +732,19 @@ controlled with tools like taskset (Linux) or cpuset (FreeBSD),
>  - with affinity restricted to 2-3, the Control Threads will end up on
>    CPU 2 (main lcore, which is the default when no CPU is available).
>  
> +Signal Safety
> +~~~~~~~~~~~~~
> +
> +The DPDK functions in general can not be safely called from a signal handler.
> +Most functions are not async-signal-safe because they can acquire locks
> +and other resources that make them nonrentrant.
> +
> +To avoid problems with unsafe functions, can be avoided if required
> +signals are blocked and a mechanism such as signalfd (Linux) is used
> +to convert the asynchronous signals into messages that are processed
> +by a EAL thread.
> +
> +
>  .. _known_issue_label:
>  
>  Known Issues
> -- 
> 2.35.1

Re: [PATCH] doc/eal: add signal safety warning

[fengchengwen]

On 2022/6/11 7:42, Tyler Retzlaff wrote:
> On Fri, Jun 10, 2022 at 08:23:43AM -0700, Stephen Hemminger wrote:
>> The DPDK is not designed to be used from a signal handler.
>> Add a notice in the documentation describing this limitation,
>> similar to Linux signal-safety manual page.
>>
>> Bugzilla ID: 1030
>> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> 
> Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>

Acked-by: Chengwen Feng <fengchengwen@huawei.com>

> 
>> ---
>>  doc/guides/prog_guide/env_abstraction_layer.rst | 13 +++++++++++++
>>  1 file changed, 13 insertions(+)
>>
>> diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
>> index 5f0748fba1c0..36ab4b5ba9b6 100644
>> --- a/doc/guides/prog_guide/env_abstraction_layer.rst
>> +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
>> @@ -732,6 +732,19 @@ controlled with tools like taskset (Linux) or cpuset (FreeBSD),
>>  - with affinity restricted to 2-3, the Control Threads will end up on
>>    CPU 2 (main lcore, which is the default when no CPU is available).
>>  
>> +Signal Safety
>> +~~~~~~~~~~~~~
>> +
>> +The DPDK functions in general can not be safely called from a signal handler.
>> +Most functions are not async-signal-safe because they can acquire locks
>> +and other resources that make them nonrentrant.
>> +
>> +To avoid problems with unsafe functions, can be avoided if required
>> +signals are blocked and a mechanism such as signalfd (Linux) is used
>> +to convert the asynchronous signals into messages that are processed
>> +by a EAL thread.
>> +
>> +
>>  .. _known_issue_label:
>>  
>>  Known Issues
>> -- 
>> 2.35.1
> 
> .
> 

Re: [PATCH] doc/eal: add signal safety warning

[Mattias Rönnblom]

On 2022-06-10 17:23, Stephen Hemminger wrote:
> The DPDK is not designed to be used from a signal handler.
> Add a notice in the documentation describing this limitation,
> similar to Linux signal-safety manual page.
> 
> Bugzilla ID: 1030
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>   doc/guides/prog_guide/env_abstraction_layer.rst | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> index 5f0748fba1c0..36ab4b5ba9b6 100644
> --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> @@ -732,6 +732,19 @@ controlled with tools like taskset (Linux) or cpuset (FreeBSD),
>   - with affinity restricted to 2-3, the Control Threads will end up on
>     CPU 2 (main lcore, which is the default when no CPU is available).
>   
> +Signal Safety
> +~~~~~~~~~~~~~
> +
> +The DPDK functions in general can not be safely called from a signal handler.
> +Most functions are not async-signal-safe because they can acquire locks
> +and other resources that make them nonrentrant.
> +
> +To avoid problems with unsafe functions, can be avoided if required
> +signals are blocked and a mechanism such as signalfd (Linux) is used
> +to convert the asynchronous signals into messages that are processed
> +by a EAL thread.
> +

Should we instead actually try to figure out what part of the API is and 
should remain async-signal-safe? And then say "nothing else is".

Without an exhaustive list, we will leave the user to guessing, or going 
into the current implementation to find out if a particular function is 
currently async-signal-safe. When that code changes in a future 
supposed-to-be-backward-compatible DPDK release, the application will break.

> +
>   .. _known_issue_label:
>   
>   Known Issues

[PATCH v2] doc/eal: add signal safety warning

[Stephen Hemminger]

The DPDK is not designed to be used from a signal handler.
Add a notice in the documentation describing this limitation,
similar to Linux signal-safety manual page.

Bugzilla ID: 1030
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
Acked-by: Chengwen Feng <fengchengwen@huawei.com>
---
 doc/guides/prog_guide/env_abstraction_layer.rst | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
index 67842ae27207..de7ee92bba39 100644
--- a/doc/guides/prog_guide/env_abstraction_layer.rst
+++ b/doc/guides/prog_guide/env_abstraction_layer.rst
@@ -818,6 +818,21 @@ Known Issues
 
   The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
 
++ signal safety
+
+  The DPDK library is not designed to be async-signal-safe.
+  Except where explicitly stated otherwise [#]_, the DPDK functions are nonreentrant and are unsafe to call from a signal handler.
+
+.. [#] Only the function ``rte_dump_stack()`` can safely be called from signal handler in this version of DPDK.
+
+.. note::
+  The kinds of issues that make DPDK functions unsafe can be understood when
+  one considers that much of the code in DPDK uses locks and other shared
+  resources. If a device driver holding a ``rte_spinlock`` is interrupted
+  by a signal and control operation is then performed that would acquire
+  the same lock, a deadlock would result.
+
+
 cgroup control
 ~~~~~~~~~~~~~~
 
-- 
2.35.1

Re: [PATCH v2] doc/eal: add signal safety warning

[Thomas Monjalon]

05/07/2022 22:44, Stephen Hemminger:
> The DPDK is not designed to be used from a signal handler.
> Add a notice in the documentation describing this limitation,
> similar to Linux signal-safety manual page.
> 
> Bugzilla ID: 1030
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> Acked-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
>  doc/guides/prog_guide/env_abstraction_layer.rst | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> index 67842ae27207..de7ee92bba39 100644
> --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> @@ -818,6 +818,21 @@ Known Issues
>  
>    The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
>  
> ++ signal safety
> +
> +  The DPDK library is not designed to be async-signal-safe.
> +  Except where explicitly stated otherwise [#]_, the DPDK functions are nonreentrant and are unsafe to call from a signal handler.
> +
> +.. [#] Only the function ``rte_dump_stack()`` can safely be called from signal handler in this version of DPDK.

Really? Are you sure?

Note: the use of [#] is probably limited to a single usage in the page?

> +
> +.. note::
> +  The kinds of issues that make DPDK functions unsafe can be understood when
> +  one considers that much of the code in DPDK uses locks and other shared
> +  resources. If a device driver holding a ``rte_spinlock`` is interrupted
> +  by a signal and control operation is then performed that would acquire
> +  the same lock, a deadlock would result.

I find this note quite confusing.

Re: [PATCH v2] doc/eal: add signal safety warning

[Stephen Hemminger]

On Mon, 11 Jul 2022 23:15:26 +0200
Thomas Monjalon <thomas@monjalon.net> wrote:

> 05/07/2022 22:44, Stephen Hemminger:
> > The DPDK is not designed to be used from a signal handler.
> > Add a notice in the documentation describing this limitation,
> > similar to Linux signal-safety manual page.
> > 
> > Bugzilla ID: 1030
> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> > Acked-by: Chengwen Feng <fengchengwen@huawei.com>
> > ---
> >  doc/guides/prog_guide/env_abstraction_layer.rst | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> > 
> > diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> > index 67842ae27207..de7ee92bba39 100644
> > --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> > +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> > @@ -818,6 +818,21 @@ Known Issues
> >  
> >    The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
> >  
> > ++ signal safety
> > +
> > +  The DPDK library is not designed to be async-signal-safe.
> > +  Except where explicitly stated otherwise [#]_, the DPDK functions are nonreentrant and are unsafe to call from a signal handler.
> > +
> > +.. [#] Only the function ``rte_dump_stack()`` can safely be called from signal handler in this version of DPDK.  
> 
> Really? Are you sure?

There are some trivial ones that are signal safe that are pure functions.
Like the bitfield and string functions.

But any function that matters such as rte_log, rte_mbuf, rte_mempool,
and any driver function are going to be problematic.

> 
> Note: the use of [#] is probably limited to a single usage in the page?

Isn't it supposed to autonumber?

> 
> > +
> > +.. note::
> > +  The kinds of issues that make DPDK functions unsafe can be understood when
> > +  one considers that much of the code in DPDK uses locks and other shared
> > +  resources. If a device driver holding a ``rte_spinlock`` is interrupted
> > +  by a signal and control operation is then performed that would acquire
> > +  the same lock, a deadlock would result.  
> 
> I find this note quite confusing.

I based it off what signal-safety says. Yes it really is that bad.

[PATCH v3] doc/eal: add signal safety warning

[Stephen Hemminger]

The DPDK is not designed to be used from a signal handler.
Add a notice in the documentation describing this limitation,
similar to Linux signal-safety manual page.

Bugzilla ID: 1030
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
Acked-by: Chengwen Feng <fengchengwen@huawei.com>
---
 doc/guides/prog_guide/env_abstraction_layer.rst | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
index 67842ae27207..de7ee92bba39 100644
--- a/doc/guides/prog_guide/env_abstraction_layer.rst
+++ b/doc/guides/prog_guide/env_abstraction_layer.rst
@@ -818,6 +818,21 @@ Known Issues
 
   The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
 
++ signal safety
+
+  The DPDK library is not designed to be async-signal-safe.
+  Except where explicitly stated otherwise [#]_, the DPDK functions are nonreentrant and are unsafe to call from a signal handler.
+
+.. [#] Only the function ``rte_dump_stack()`` can safely be called from signal handler in this version of DPDK.
+
+.. note::
+  The kinds of issues that make DPDK functions unsafe can be understood when
+  one considers that much of the code in DPDK uses locks and other shared
+  resources. If a device driver holding a ``rte_spinlock`` is interrupted
+  by a signal and control operation is then performed that would acquire
+  the same lock, a deadlock would result.
+
+
 cgroup control
 ~~~~~~~~~~~~~~
 
-- 
2.35.1

[PATCH v4] doc/eal: add signal safety warning

[Stephen Hemminger]

The DPDK is not designed to be used from a signal handler.
Add a notice in the documentation describing this limitation,
similar to Linux signal-safety manual page.

Bugzilla ID: 1030
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
Acked-by: Chengwen Feng <fengchengwen@huawei.com>
---
v4 - add more functions and clarify

v3 - mistake (ignore it)

 .../prog_guide/env_abstraction_layer.rst      | 70 +++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
index 67842ae27207..35fbebe1be04 100644
--- a/doc/guides/prog_guide/env_abstraction_layer.rst
+++ b/doc/guides/prog_guide/env_abstraction_layer.rst
@@ -818,6 +818,76 @@ Known Issues
 
   The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
 
+Signal Safety
+~~~~~~~~~~~~~
+
+  The Posix API defines an async-signal-safe function as one that can be safely
+  called from with a signal handler. Many DPDK functions are non-reentrant and
+  therefore are unsafe to call from a signal handler.
+
+  The kinds of issues that make DPDK functions unsafe can be understood when
+  one considers that much of the code in DPDK uses locks and other shared
+  resources. For example, calling ``rte_mempool_lookup()`` from a signal
+  would deadlock if the signal happened during previous call ``rte_mempool``
+  routines.
+
+  Other functions are not signal safe because they use one or more
+  library routines that are not themselves signal safe.
+  For example, calling ``rte_panic()`` is not safe in a signal handler
+  because it uses ``rte_log()`` and ``rte_log()`` calls the
+  ``syslog()`` library function which is in the list of
+  signal safe functions in
+  `Signal-Safety manual page <https://man7.org/linux/man-pages/man7/signal-safety.7.html>`_.
+
+  The set of functions that are expected to be async-signal-safe in DPDK
+  is shown in the following table. The functions not otherwise noted
+  are not async-signal-safe.
+
+.. csv-table:: **Signal Safe Functions**
+   :header: "Function"
+   :widths: 32
+
+   rte_dump_stack
+   rte_eal_get_lcore_state
+   rte_eal_get_runtime_dir
+   rte_eal_has_hugepages
+   rte_eal_has_pci
+   rte_eal_lcore_role
+   rte_eal_process_type
+   rte_eal_using_phys_addrs
+   rte_get_hpet_cycles
+   rte_get_hpet_hz
+   rte_get_main_lcore
+   rte_get_next_lcore
+   rte_get_tsc_hz
+   rte_hypervisor_get
+   rte_hypervisor_get_name
+   rte_lcore_count
+   rte_lcore_cpuset
+   rte_lcore_has_role
+   rte_lcore_index
+   rte_lcore_is_enabled
+   rte_lcore_to_cpu_id
+   rte_lcore_to_socket_id
+   rte_log_get_global_level
+   rte_log_get_level
+   rte_memory_get_nchannel
+   rte_memory_get_nrank
+   rte_reciprocal_value
+   rte_reciprocal_value_u64
+   rte_socket_count
+   rte_socket_id
+   rte_socket_id_by_idx
+   rte_strerror
+   rte_strscpy
+   rte_strsplit
+   rte_sys_gettid
+   rte_uuid_compare
+   rte_uuid_is_null
+   rte_uuid_parse
+   rte_uuid_unparse
+
+
 cgroup control
 ~~~~~~~~~~~~~~
 
-- 
2.35.1

Re: [PATCH v2] doc/eal: add signal safety warning

[Stephen Hemminger]

On Mon, 11 Jul 2022 23:15:26 +0200
Thomas Monjalon <thomas@monjalon.net> wrote:

> 05/07/2022 22:44, Stephen Hemminger:
> > The DPDK is not designed to be used from a signal handler.
> > Add a notice in the documentation describing this limitation,
> > similar to Linux signal-safety manual page.
> > 
> > Bugzilla ID: 1030
> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> > Acked-by: Chengwen Feng <fengchengwen@huawei.com>
> > ---
> >  doc/guides/prog_guide/env_abstraction_layer.rst | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> > 
> > diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> > index 67842ae27207..de7ee92bba39 100644
> > --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> > +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> > @@ -818,6 +818,21 @@ Known Issues
> >  
> >    The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
> >  
> > ++ signal safety
> > +
> > +  The DPDK library is not designed to be async-signal-safe.
> > +  Except where explicitly stated otherwise [#]_, the DPDK functions are nonreentrant and are unsafe to call from a signal handler.
> > +
> > +.. [#] Only the function ``rte_dump_stack()`` can safely be called from signal handler in this version of DPDK.  
> 
> Really? Are you sure?
> 
> Note: the use of [#] is probably limited to a single usage in the page?

Yes. this is true, please apply this patch.

It is not safe to call functions that do any of the following:
	printf
	malloc
according to Linux async-signal-safe documentation

And because these all have locking or equivalent atomic the following
in DPDK are unsafe.

	rte_ring
	rte_timer
	rte_spinlock, rte_rwlock, ...
	any PMD operations

Re: [PATCH v4] doc/eal: add signal safety warning

[Stephen Hemminger]

On Mon, 11 Jul 2022 16:04:48 -0700
Stephen Hemminger <stephen@networkplumber.org> wrote:

> The DPDK is not designed to be used from a signal handler.
> Add a notice in the documentation describing this limitation,
> similar to Linux signal-safety manual page.
> 
> Bugzilla ID: 1030
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> Acked-by: Chengwen Feng <fengchengwen@huawei.com>

There have been reports of this problem, multiple ack's of this patch
but it is still not merged.  It documents a real problem that will trap
users.

Re: [PATCH v4] doc/eal: add signal safety warning

[David Marchand]

On Tue, Jul 12, 2022 at 1:05 AM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> The DPDK is not designed to be used from a signal handler.
> Add a notice in the documentation describing this limitation,
> similar to Linux signal-safety manual page.
>
> Bugzilla ID: 1030

> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> Acked-by: Chengwen Feng <fengchengwen@huawei.com>

Applied, thanks.


-- 
David Marchand