[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 at networkplumber.org>
Acked-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
Acked-by: Chengwen Feng <fengchengwen at 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