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Tony Finch 9b7aa536ba QSBR: safe memory reclamation for lock-free data structures 
This "quiescent state based reclamation" module provides support for
the qp-trie module in dns/qp. It is a replacement for liburcu, written
without reference to the urcu source code, and in fact it works in a
significantly different way.

A few specifics of BIND make this variant of QSBR somewhat simpler:

  * We can require that wait-free access to a qp-trie only happens in
    an isc_loop callback. The loop provides a natural quiescent state,
    after the callbacks are done, when no qp-trie access occurs.

  * We can dispense with any API like rcu_synchronize(). In practice,
    it takes far too long to wait for a grace period to elapse for each
    write to a data structure.

  * We use the idea of "phases" (aka epochs or eras) from EBR to
    reduce the amount of bookkeeping needed to track memory that is no
    longer needed, knowing that the qp-trie does most of that work
    already.

I considered hazard pointers for safe memory reclamation. They have
more read-side overhead (updating the hazard pointers) and it wasn't
clear to me how to nicely schedule the cleanup work. Another
alternative, epoch-based reclamation, is designed for fine-grained
lock-free updates, so it needs some rethinking to work well with the
heavily read-biased design of the qp-trie. QSBR has the fastest read
side of the basic SMR algorithms (with no barriers), and fits well
into a libuv loop. More recent hybrid SMR algorithms do not appear to
have enough benefits to justify the extra complexity.
2023-02-23 15:57:53 +00:00
..
include QSBR: safe memory reclamation for lock-free data structures 2023-02-23 15:57:53 +00:00
netmgr remove isc_task completely 2023-02-16 18:35:32 +01:00
.gitignore
aes.c Remove EVP_CIPHER_CTX_new() and EVP_CIPHER_CTX_free() shims 2022-03-02 10:48:09 +00:00
ascii.c Consolidate some ASCII tables in isc/ascii and isc/hex 2022-09-12 12:18:57 +01:00
assertions.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
async.c Use atomic stack for async job queue 2023-02-22 16:13:37 +00:00
backtrace.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
base32.c Remove use of the inline keyword used as suggestion to compiler 2022-03-25 08:33:43 +01:00
base64.c Remove use of the inline keyword used as suggestion to compiler 2022-03-25 08:33:43 +01:00
commandline.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
condition.c De-duplicate some calls to strerror_r() 2022-10-17 11:58:26 +01:00
counter.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
crc64.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
dir.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
entropy.c Switch the CSPRNG function from RAND_bytes() to uv_random() 2022-09-26 15:13:11 +02:00
errno.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
errno2result.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
errno2result.h Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
error.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
file.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
fsaccess.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
fsaccess_common.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
fsaccess_common_p.h Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
getaddresses.c Move bind9_getaddresses() to isc_getaddresses() 2023-02-21 13:12:26 +00:00
hash.c Improve reporting for pthread_once errors 2022-10-14 16:39:21 +02:00
hashmap.c Add isc_hashmap_find() DbC check for valuep 2023-02-15 09:30:04 +01:00
heap.c Update sources to Clang 15 formatting 2022-11-29 08:54:34 +01:00
hex.c Consolidate some ASCII tables in isc/ascii and isc/hex 2022-09-12 12:18:57 +01:00
hmac.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
ht.c Update sources to Clang 15 formatting 2022-11-29 08:54:34 +01:00
httpd.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
interfaceiter.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
iterated_hash.c Require C11 thread_local keyword and <threads.h> header 2023-02-08 21:33:23 +01:00
jemalloc_shim.h Fix ISC_MEM_ZERO on allocators with malloc_usable_size() 2023-02-06 11:21:12 +00:00
job.c Use atomic stack for async job queue 2023-02-22 16:13:37 +00:00
job_p.h New event loop handling API 2022-08-25 12:24:29 +02:00
lex.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
lib.c remove isc_bind9 variable 2023-02-09 18:00:13 +00:00
log.c Remove do-nothing header <isc/stat.h> 2023-02-15 16:44:47 +00:00
loop.c QSBR: safe memory reclamation for lock-free data structures 2023-02-23 15:57:53 +00:00
loop_p.h QSBR: safe memory reclamation for lock-free data structures 2023-02-23 15:57:53 +00:00
Makefile.am QSBR: safe memory reclamation for lock-free data structures 2023-02-23 15:57:53 +00:00
managers.c remove isc_task completely 2023-02-16 18:35:32 +01:00
md.c Avoid implicit algorithm fetch for OpenSSL EVP_MD family 2023-01-18 18:32:57 +01:00
mem.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
mem_p.h Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
meminfo.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
mutex.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
mutex_p.h Use library constructor to create default mutex attr once 2022-07-13 13:19:32 +02:00
mutexblock.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
net.c Remove do-nothing header <isc/netdb.h> 2023-02-15 16:44:47 +00:00
netaddr.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
netscope.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
nonce.c Switch the CSPRNG function from RAND_bytes() to uv_random() 2022-09-26 15:13:11 +02:00
openssl_shim.c Do not provide a shim for SSL_SESSION_is_resumable() 2022-05-23 18:25:18 +03:00
openssl_shim.h Do not provide a shim for SSL_SESSION_is_resumable() 2022-05-23 18:25:18 +03:00
os.c Remove use of the inline keyword used as suggestion to compiler 2022-03-25 08:33:43 +01:00
os_p.h Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
parseint.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
picohttpparser.c Update sources to Clang 15 formatting 2022-11-29 08:54:34 +01:00
picohttpparser.h Add picohttpparser.{c.h} from https://github.com/h2o/picohttpparser 2022-10-14 11:26:54 +02:00
portset.c Use designated initializers instead of memset()/MEM_ZERO for structs 2022-10-05 16:44:05 +02:00
qsbr.c QSBR: safe memory reclamation for lock-free data structures 2023-02-23 15:57:53 +00:00
quota.c REQUIRE should not have side effects 2022-07-05 12:22:55 -07:00
radix.c Update sources to Clang 15 formatting 2022-11-29 08:54:34 +01:00
random.c Switch the CSPRNG function from RAND_bytes() to uv_random() 2022-09-26 15:13:11 +02:00
random_p.h Move random number re-seeding out of the hot path 2022-09-19 16:27:12 +02:00
ratelimiter.c remove isc_task completely 2023-02-16 18:35:32 +01:00
regex.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
region.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
result.c Refactor isc_nm_xfr_allowed() 2023-01-19 10:24:08 +00:00
rwlock.c Add the reader-writer synchronization with modified C-RW-WP 2023-02-15 09:30:04 +01:00
safe.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
serial.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
signal.c New event loop handling API 2022-08-25 12:24:29 +02:00
siphash.c Accept 'in=NULL' with 'inlen=0' in isc_{half}siphash24 2023-01-10 17:52:56 +11:00
sockaddr.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
stats.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
stdio.c Remove do-nothing header <isc/stat.h> 2023-02-15 16:44:47 +00:00
stdtime.c Deduplicate time unit conversion factors 2022-11-25 13:23:36 +00:00
string.c Explain <isc/strerr.h> a little more 2023-02-15 16:44:09 +00:00
symtab.c Consolidate some ASCII tables in isc/ascii and isc/hex 2022-09-12 12:18:57 +01:00
syslog.c Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
tests Move all the unit tests to /tests/<libname>/ 2022-05-28 14:53:02 -07:00
thread.c Fix error reporting for POSIX Threads functions 2022-09-09 20:25:47 +02:00
tid.c Require C11 thread_local keyword and <threads.h> header 2023-02-08 21:33:23 +01:00
time.c Remove do-nothing header <isc/print.h> 2023-02-15 16:44:47 +00:00
timer.c remove isc_task completely 2023-02-16 18:35:32 +01:00
tls.c Add the reader-writer synchronization with modified C-RW-WP 2023-02-15 09:30:04 +01:00
tm.c Consolidate some ASCII tables in isc/ascii and isc/hex 2022-09-12 12:18:57 +01:00
trampoline.c Use thread_local EVP_MD_CTX in isc_iterated_hash() 2023-01-18 19:36:21 +01:00
trampoline_p.h Update the copyright information in all files in the repository 2022-01-11 09:05:02 +01:00
url.c Update sources to Clang 15 formatting 2022-11-29 08:54:34 +01:00
utf8.c Update sources to Clang 15 formatting 2022-11-29 08:54:34 +01:00
uv.c Add and use semantic patch to replace isc_mem_get/allocate+memset 2022-10-05 16:44:05 +02:00
work.c New event loop handling API 2022-08-25 12:24:29 +02:00
xml.c Add autoconf option to enable memory leak detection in libraries 2022-09-27 17:53:04 +02:00