osmocom-sdr November 2022

osmocom-sdr@lists.osmocom.org

2 participants
2 discussions

[PATCH] Fix signal handler from getting stuck in an endless loop

by Tobias Girstmair

The signal handler for SIGINT/TERM/QUIT and, importantly, SIGPIPE tries to write an informational message to stderr. When however stderr is redirected to a closed pipe, this will cause (another) SIGPIPE, and in turn the signal handler will get called again, and again and again. Since we intend to exit rtl_fm anyways, we can just ignore this signal from this point on. --- Here is a small test program to verify the bug. from subprocess import Popen, PIPE p = Popen("rtl_test", stderr=PIPE) # sighandler is set up after rtlsdr_open() call, so read past that while p.stderr.readline()[:8] != b"Sampling": pass p.stderr.close() p.terminate() # SIGTERM -> sighandler() -> fprintf(stderr) -> SIGPIPE! Note that the signal handler is not set up immediately, but only after rtlsdr_open() is called. Due to line buffering/flushing on stderr, we must read from the pipe or rtl_* will stall and SIGTERM/PIPE will still be handled by the SIG_DFL, not triggering the write to the broken pipe. And in case someone is wondering: Using signal(2) instead of sigaction(2) is OK, as long as it only sets to SIG_DFL or SIG_IGN. src/rtl_adsb.c | 1 + src/rtl_fm.c | 1 + src/rtl_power.c | 1 + src/rtl_sdr.c | 1 + src/rtl_tcp.c | 1 + src/rtl_test.c | 1 + 6 files changed, 6 insertions(+) diff --git a/src/rtl_adsb.c b/src/rtl_adsb.c index 7aea8dd..8119ac8 100644 --- a/src/rtl_adsb.c +++ b/src/rtl_adsb.c @@ -123,6 +123,7 @@ sighandler(int signum) #else static void sighandler(int signum) { + signal(SIGPIPE, SIG_IGN); fprintf(stderr, "Signal caught, exiting!\n"); do_exit = 1; rtlsdr_cancel_async(dev); diff --git a/src/rtl_fm.c b/src/rtl_fm.c index 7c84332..037793c 100644 --- a/src/rtl_fm.c +++ b/src/rtl_fm.c @@ -246,6 +246,7 @@ sighandler(int signum) #else static void sighandler(int signum) { + signal(SIGPIPE, SIG_IGN); fprintf(stderr, "Signal caught, exiting!\n"); do_exit = 1; rtlsdr_cancel_async(dongle.dev); diff --git a/src/rtl_power.c b/src/rtl_power.c index 6204de2..df3ceb7 100644 --- a/src/rtl_power.c +++ b/src/rtl_power.c @@ -195,6 +195,7 @@ sighandler(int signum) #else static void sighandler(int signum) { + signal(SIGPIPE, SIG_IGN); do_exit++; multi_bail(); } diff --git a/src/rtl_sdr.c b/src/rtl_sdr.c index e6537ca..2c93b57 100644 --- a/src/rtl_sdr.c +++ b/src/rtl_sdr.c @@ -74,6 +74,7 @@ sighandler(int signum) #else static void sighandler(int signum) { + signal(SIGPIPE, SIG_IGN); fprintf(stderr, "Signal caught, exiting!\n"); do_exit = 1; rtlsdr_cancel_async(dev); diff --git a/src/rtl_tcp.c b/src/rtl_tcp.c index 84f5591..8781ba9 100644 --- a/src/rtl_tcp.c +++ b/src/rtl_tcp.c @@ -144,6 +144,7 @@ sighandler(int signum) #else static void sighandler(int signum) { + signal(SIGPIPE, SIG_IGN); fprintf(stderr, "Signal caught, exiting!\n"); rtlsdr_cancel_async(dev); do_exit = 1; diff --git a/src/rtl_test.c b/src/rtl_test.c index 9b44097..b7f46ea 100644 --- a/src/rtl_test.c +++ b/src/rtl_test.c @@ -115,6 +115,7 @@ sighandler(int signum) #else static void sighandler(int signum) { + signal(SIGPIPE, SIG_IGN); fprintf(stderr, "Signal caught, exiting!\n"); do_exit = 1; rtlsdr_cancel_async(dev); -- 2.38.1

1 year, 4 months

A Bit Of a Mess

by Kevin Utzy

I am trying to go back and simply install gqrx on Liux Mint v21 Vanessa (Ubuntu Jammy) using an RTL-SDR V3. It all started I believe when I tried to install SDR++ building it from source. I install osmo_sdr and gr-osmosdr. I have worked my way through and deleted some of the issues, the last one being getting rid of the osmo_sdr binary. Deleting that removed the error I was getting with the libgnuradio-osmosdr.0.2.0 (it was showing libgnuradio-osmosdr.0.2.0 (build 0.3build53 or something). I am now getting an error running gqrx is "gqrx: error while loading shared libraries: libgnuradio-blocks.so.3.10.1: cannot open shared object file: No such file or directory". Some fragment of something I uninstalled incorrectly is causing gqrx distribution to think that this is already installed. If I could figure out what that is, it would be helpful. The reason I am posting this here is because it started I believe when I installed either osmo_sdr or gr-osmosdr. Thank you. Kevin

1 year, 5 months

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

osmocom-sdr November 2022