Re: [dpdk-dev] [PATCH v2 1/6] eal: introduce oops handling API

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 17 Aug 2021 13:08:46 +0530
Jerin Jacob <jerinjacobk@gmail.com> wrote:

> On Tue, Aug 17, 2021 at 9:23 AM Stephen Hemminger
> <stephen@networkplumber.org> wrote:
> >
> > On Tue, 17 Aug 2021 08:57:18 +0530
> > <jerinj@marvell.com> wrote:
> >  
> > > From: Jerin Jacob <jerinj@marvell.com>
> > >
> > > Introducing oops handling API with following specification
> > > and enable stub implementation for Linux and FreeBSD.
> > >
> > > On rte_eal_init() invocation, the EAL library installs the
> > > oops handler for the essential signals.
> > > The rte_oops_signals_enabled() API provides the list
> > > of signals the library installed by the EAL.  
> >
> > This is a big change, and many applications already handle these
> > signals themselves. Therefore adding this needs to be opt-in
> > and not enabled by default.  
> 
> In order to avoid every application explicitly register this
> sighandler and to cater to the
> co-existing application-specific signal-hander usage.
> The following design has been chosen. (It is mentioned in the commit log,
> I will describe here for more clarity)
> 
> Case 1:
> a) The application installs the signal handler prior to rte_eal_init().
> b) Implementation stores the application-specific signal and replace a
> signal handler as oops eal handler
> c) when application/DPDK get the segfault, the default EAL oops
> handler gets invoked
> d) Then it dumps the EAL specific message, it calls the
> application-specific signal handler
> installed in step 1 by application. This avoids breaking any contract
> with the application.
> i.e Behavior is the same current EAL now.
> That is the reason for not using SA_RESETHAND(which call SIG_DFL after
> eal oops handler instead
> application-specific handler)
> 
> Case 2:
> a) The application install the signal handler after rte_eal_init(),
> b) EAL hander get replaced with application handle then the application can call
> rte_oops_decode() to decode.
> 
> In order to cater the above use case, rte_oops_signals_enabled() and
> rte_oops_decode()
> provided.
> 
> Here we are not breaking any contract with the application.
> Do you have concerns about this design?

In our application as a service it is important not to do any backtrace
in production. We rely on other infrastructure to process coredumps.

This should be controlled enabled by a command line argument.