Apache httpd 2.4.34 couldn't receive signal SIGTERM on SuSE 15

Question

I have install apache httpd 2.4.34 on SLES 15, and there are six httpd processes running.

When I send signal SIGTERM to httpd process, all the six httpd process couldn't receive signal SIGTERM (I had gdb attched httpd process to catch signal SIGTERM), but I find kill 15 11143 return 0 via command strace. But httpd could reiveive signal SIGKILL, it's very strange.

And apache httpd 2.4.34 running on other platform(SLES12, SLES11, RHEL7) could reiveive and handle signal SIGTERM normally.

Does anyone encounter this phenomenon?

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# cat /etc/os-release
NAME="SLES"
VERSION="15"
VERSION_ID="15"
PRETTY_NAME="SUSE Linux Enterprise Server 15"
ID="sles"
ID_LIKE="suse"
ANSI_COLOR="0;32"
CPE_NAME="cpe:/o:suse:sles:15"

#uname -a
Linux linux-iv0h 4.12.14-23-default #1 SMP Tue May 29 21:04:44 UTC 2018 (cd0437b) x86_64 x86_64 x86_64 GNU/Linux

#ps aux|grep httpd
root     11143  0.0  0.6  23612  6380 ?        Ss   04:33   0:00 ./httpd
nobody   11144  0.0  0.3  23612  3248 ?        S    04:33   0:00 ./httpd
nobody   11145  0.0  0.3  23612  3248 ?        S    04:33   0:00 ./httpd
nobody   11146  0.0  0.3  23612  3248 ?        S    04:33   0:00 ./httpd
nobody   11147  0.0  0.3  23612  3248 ?        S    04:33   0:00 ./httpd
nobody   11148  0.0  0.3  23612  3248 ?        S    04:33   0:00 ./httpd
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