Re: [PATCH 00/13] make signal handlers async-signal-safe

[Bruce Richardson <bruce.richardson@intel.com>]

On Sun, Sep 06, 2026 at 04:24:35PM -0700, Stephen Hemminger wrote:
> Signal handlers may only call the functions listed in signal-safety(7).
> Many DPDK examples ignored this and did printf() a "preparing to exit"
> message before setting the quit flag. A signal during another printf
> call can deadlock. And some of the programs did even more
> unsafe things.
> 
> GCC 14 -fanalyzer reports these:
> 
>   warning: call to 'printf' from within signal handler [CWE-479]
> 	[-Wanalyzer-unsafe-call-within-signal-handler]
> 
> The fix is the same throughout: the handler only sets the existing
> volatile flag, and any real work moves to the main loop or to main()
> after the lcores are joined. The message is dropped; the user pressed ^C
> and knows a signal was sent.
> 
> Patches 1-2 only delete the printf(). Patches 3-13 also relocate work
> that was being done in the handler.
> 
> Behaviour changes worth review:
> 
> - examples/ntb: SIGINT used to printf(), restore SIG_DFL and re-raise,
>   killing the process without stopping the forwarding lcores or closing
>   the devices. It now sets the per-lcore stopped flag, so SIGINT stops
>   forwarding and returns to the ntb> prompt; quit does the teardown.
> 
> - examples/vdpa: the teardown moved to main() now also closes the vDPA
>   devices when leaving interactive mode, which was missing before.
> 
> - examples/eventdev_pipeline: the second-signal escape hatch becomes
>   _exit() instead of rte_exit(), the --dump-dev exit dump moves to
>   main() (and uses the real dev_id rather than a hardcoded 0), and
>   SIGTSTP now sets cdata.dump_dev_signal, which schedule_devices()
>   already drained but nothing ever set. The SIGTSTP dump therefore
>   requires a scheduler lcore.
> 
> Only examples/ethtool and examples/vmdq_dcb carry a Fixes: tag; the rest
> remove an unsafe call that has not been seen to deadlock in practice and
> are cleanups rather than backport material.
> 
> Applications outside the analyzer's reach likely have the same pattern;
> this covers what GCC flagged, plus eventdev_pipeline found by inspection.
> 
> Build tested with GCC 14 -fanalyzer; the warnings are gone for the files
> touched.
> 
> Stephen Hemminger (13):
>   graph: do not call printf in signal
>   examples: remove printf from signal handler
>   examples/vmdq: do not print from signal handler
>   examples/symmetric_mp: do not print or exit in handler
>   examples/vdpa: make signal handler safe
>   examples/vhost: make signal handler safe
>   examples/vhost_blk: do not tear down from signal handler
>   examples/ntb: do not print and re-raise from signal handler
>   examples/ipsecgw: do not print from signal handler
>   examples/l2fwd-macsec: remove print in signal handler
>   examples/ethtool: fix exit flag and unchecked cmdline
>   examples/vmdq_dcb: allow exit on signal
>   examples/eventdev_pipeline: make signal handler safe
> 
Series-Acked-by: Bruce Richardson <bruce.richardson@intel.com>