wait skips signals but first one

[Mykyta Dorokhin]

From: kit-D@ukr.net
To: bug-bash@gnu.org
Subject: wait skips signals but first one

Configuration Information [Automatically generated, do not change]:
Machine: arm
OS: linux-gnueabi
Compiler: arm-mydistro-linux-gnueabi-gcc  -mthumb -mfpu=neon -mfloat-abi=hard 
-mcpu=cortex-a7
Compilation CFLAGS:  -O2 -pipe -g -feliminate-unused-debug-types  
-DNON_INTERACTIVE_LOGIN_SHELLS -DHEREDOC_PIPESIZE=65536 
-DBRACKETED_PASTE_DEFAULT=0
uname output: Linux mtcap3 5.15.87 #1 PREEMPT Tue Sep 19 16:09:21 UTC 2023 
armv7l GNU/Linux
Machine Type: arm-mydistro-linux-gnueabi

Bash Version: 5.1
Patch Level: 16
Release Status: release

Description:


I'm working on a custom project within the Yocto framework. After a recent 
build system update, the bash
version updated to 5.1.16. Subsequently, I've noticed peculiar side effects 
related to using 'wait' and signals.
Below is a script demonstrating the issue.

The problem lies in the fact that, in the case of waiting on 'wait' in the 
script, only the first signal
interrupts 'wait'; subsequent signals of the same type do not interrupt 'wait', 
and it remains blocked.

I manually switched bash versions and compiled a table (bash version - Yocto 
version):

5.0.18 (dunfell): No issues
5.1.4 (hardknott): Has issues
5.1.8 (honister): Has issues
5.1.16 (kirkstone): Has issues
5.2.21 (master): Has issues

Meanwhile, in my home desktop distribution, Ubuntu 22.04, I tested the same 
scenario, and everything works correctly; signals are processed as expected.

My assumption is that the problem may be related to my Yocto build being 
intended for a 32-bit device, and perhaps the bug only manifests in this case.

I consider this a significant issue. Could you confirm whether any testing has 
been conducted on 32-bit platforms,
as it seems that everything works correctly on 64-bit desktops?

Repeat-By:

Here is a simple script:

#!/bin/bash

trap 'echo ">>> TRAPPED HUP <<<"' HUP
trap 'echo ">>> TRAPPED USR1 <<<"' USR1

while true; do
 echo "Iteration"
 /bin/sleep 15 &
 wait $!
done


When I send HUP or USR1 multiple times I see the TRAPPED message only once.

strace says:

rt_sigprocmask(SIG_BLOCK, [CHLD], [HUP USR1 CHLD], 8) = 0

Meaning that HUP and USR1 remain blocked.