Correctly handle SIGINT/stop signal in nr-softmodem

• Correctly handle SIGINT, so that the nr-softmodem stops regularly
• Implement abortTpool() to stop the complete Tpool (the previous abortTpool() function has been renamed to abortTpoolJob())
• Implement abortNotifiedFIFO() to unblock an existing FIFO (the previous abortNotifiedFIFO() function has been renamed to abortNotifiedFIFOJob())
• Improve the Tpool documentation markup, see thread-pool.md
• Correctly stop the USRP: it is possible to start the nr/lte-softmodem immediately after it has been stopped, without the need to wait: should solve #519 (closed)
• Some memory fixes: on L1, for NFAPI PUCCH PDUs, and a big memory leak for UP traffic in UL at the GTP

changed milestone to %REVIEW_CAN_START

added 5G-NR label

requested review from @lthomas

assigned to @luis_pereira87

OAI RAN-CI-develop build (3427): Some Changed files in Merge Request DO NOT follow OAI Formatting Rules

OAI RAN-CI-develop build (3427): failed (https://open5glab.eurecom.fr:8083/jenkins/job/RAN-CI-develop/3427/)

OAI RAN-Container-Parent build (2041): failed (https://jenkins-oai.eurecom.fr/job/RAN-Container-Parent/2041/)

changed the description

added 12 commits

• 842bb0f6 - Avoid additional malloc() for queues and Tpool
• 690b5828 - Replace sleep by mutex in itti_wait_tasks_end()
• 1d9af732 - Threading/memory improvements at nr-softmodem end
• e452656d - Don't stop nr-softmodem on FEP thread exit cond
• ffe3ce08 - threadCreate(): don't create detached threads
• 6398a417 - Implement abortTpool()
• afadc356 - Rewrite kill_NR_RU_proc() and reuse functions
• dde73bd8 - Don't call trx_end_func() at nr-softmodem, is done in ru_thread()
• f426085a - Free USRP objects in trx_usrp_end()
• dcc21fa8 - Close rfsimulator sockets
• 6c54344d - Check oai_exit in wait_on_condition() and friends, no volatile
• d5ae85ff - Drop empty logging statement

Compare with previous version

OAI RAN-CI-develop build (3431): Some Changed files in Merge Request DO NOT follow OAI Formatting Rules

OAI RAN-Container-Parent build (2045): failed (https://jenkins-oai.eurecom.fr/job/RAN-Container-Parent/2045/)

added 2 commits

• 6137e5b2 - Check oai_exit in wait_on_condition() and friends, no volatile
• 7f996acf - Drop empty logging statement

Compare with previous version

OAI RAN-CI-develop build (3431): failed (https://open5glab.eurecom.fr:8083/jenkins/job/RAN-CI-develop/3431/)

OAI RAN-CI-develop build (3432): Some Changed files in Merge Request DO NOT follow OAI Formatting Rules

OAI RAN-Container-Parent build (2046): failed (https://jenkins-oai.eurecom.fr/job/RAN-Container-Parent/2046/)

OAI RAN-CI-develop build (3432): failed (https://open5glab.eurecom.fr:8083/jenkins/job/RAN-CI-develop/3432/)

Hi @schmidtr in this MR, gNB stalls for me when pushing uplink with poor connection (with ulsch retransmissions)

This commit seems to be the root cause: 6398a417

function like kill_feptx_thread() sends a posix signal to the thread,
processed by wait_on_condition() that returns as a normal processing (returns 0 even in oai_exit is true)
so, it makes a segv because the rxdata/txdata... buffers can already be freed

changed milestone to %REVIEW_IN_PROGRESS

added 365 commits

• 7f996acf...12a23fb1 - 352 commits from branch develop
• f7409e9b - Rename abortTpool() to abortTpoolJob(), fix doc
• 40d72adb - Avoid additional malloc() for queues and Tpool
• 44411cee - Replace sleep by mutex in itti_wait_tasks_end()
• 912fb4a3 - Threading/memory improvements at nr-softmodem end
• b44bdfff - Don't stop nr-softmodem on FEP thread exit cond
• 38206bf3 - threadCreate(): don't create detached threads
• d97e8a78 - Implement abortTpool()
• 0773b562 - Rewrite kill_NR_RU_proc() and reuse functions
• 1dd2ea0a - Don't call trx_end_func() at nr-softmodem, is done in ru_thread()
• dd42db52 - Free USRP objects in trx_usrp_end()
• 3c9e87f6 - Close rfsimulator sockets
• 008a1cd0 - Check oai_exit in wait_on_condition() and friends, no volatile
• 229655e4 - Drop empty logging statement

Compare with previous version