[v4] doc/eal: add signal safety warning
Checks
Commit Message
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(+)
Comments
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.
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.
@@ -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
~~~~~~~~~~~~~~