Paolo Bonzini 050de36b13 coroutine-lock: Reimplement CoRwlock to fix downgrade bug ... An invariant of the current rwlock is that if multiple coroutines hold a reader lock, all must be runnable. The unlock implementation relies on this, choosing to wake a single coroutine when the final read lock holder exits the critical section, assuming that it will wake a coroutine attempting to acquire a write lock. The downgrade implementation violates this assumption by creating a read lock owning coroutine that is exclusively runnable - any other coroutines that are waiting to acquire a read lock are *not* made runnable when the write lock holder converts its ownership to read only. More in general, the old implementation had lots of other fairness bugs. The root cause of the bugs was that CoQueue would wake up readers even if there were pending writers, and would wake up writers even if there were readers. In that case, the coroutine would go back to sleep *at the end* of the CoQueue, losing its place at the head of the line. To fix this, keep the queue of waiters explicitly in the CoRwlock instead of using CoQueue, and store for each whether it is a potential reader or a writer. This way, downgrade can look at the first queued coroutines and wake it only if it is a reader, causing all other readers in line to be released in turn. Reported-by: David Edmondson <david.edmondson@oracle.com> Reviewed-by: David Edmondson <david.edmondson@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20210325112941.365238-5-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>		2021-03-31 10:44:21 +01:00
..
aio-posix.c	qmp: Move dispatcher to a coroutine	2020-10-09 07:08:20 +02:00
aio-posix.h	aio-posix: remove idle poll handlers to improve scalability	2020-03-09 16:45:16 +00:00
aio-wait.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
aio-win32.c	qmp: fix aio_poll() assertion failure on Windows	2020-11-03 16:24:56 +01:00
aiocb.c	block: move AioContext, QEMUTimer, main-loop to libqemuutil	2017-02-21 11:14:07 +00:00
async.c	util/async: Add aio_co_reschedule_self()	2020-10-09 07:08:20 +02:00
atomic64.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
base64.c	nomaintainer: Fix Lesser GPL version number	2020-11-15 17:04:40 +01:00
bitmap.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
bitops.c	avoid TABs in files that only contain a few	2019-01-11 15:46:56 +01:00
block-helpers.c	block: move logical block size check function to a common utility function	2020-10-23 13:42:16 +01:00
block-helpers.h	block: move logical block size check function to a common utility function	2020-10-23 13:42:16 +01:00
buffer.c	nomaintainer: Fix Lesser GPL version number	2020-11-15 17:04:40 +01:00
bufferiszero.c	util/bufferiszero: improve avx2 accelerator	2020-04-01 14:24:03 -04:00
cacheflush.c	util/cacheflush: Fix error generated by clang	2021-01-21 13:00:41 +01:00
cacheinfo.c	util: Enhance flush_icache_range with separate data pointer	2021-01-07 05:09:41 -10:00
compatfd.c	util/compatfd.c: Only include <sys/syscall.h> if CONFIG_SIGNALFD	2020-07-13 14:36:10 +01:00
coroutine-sigaltstack.c	coroutine-sigaltstack: Add SIGUSR2 mutex	2021-01-26 14:36:37 +01:00
coroutine-ucontext.c	Remove the CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE switch	2020-07-13 11:40:52 +02:00
coroutine-win32.c	coroutine: add a macro for the coroutine stack size	2016-09-29 14:13:39 +02:00
crc32c.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
crc-ccitt.c	util: Add CRC16 (CCITT) calculation routines	2021-01-24 20:10:54 +01:00
cutils.c	utils: Work around mingw strto*l bug with 0x	2021-03-24 14:25:41 +00:00
dbus.c	util: add dbus helper unit	2020-01-06 18:41:32 +04:00
drm.c	util/drm: make portable by avoiding struct dirent d_type	2020-07-13 14:36:10 +01:00
envlist.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
error.c	error: make Error **errp const where it is appropriate	2019-12-18 08:36:16 +01:00
event_notifier-posix.c	event_notifier: Set ->initialized earlier in event_notifier_init()	2021-02-16 17:15:39 +01:00
event_notifier-win32.c	Revert "qemu: add a cleanup callback function to EventNotifier"	2018-01-24 19:20:19 +02:00
fdmon-epoll.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
fdmon-io_uring.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
fdmon-poll.c	fdmon-poll: reset npfd when upgrading to fdmon-epoll	2020-09-23 13:45:52 +01:00
fifo8.c	utils/fifo8: change fatal errors from abort() to assert()	2021-02-07 20:38:20 +00:00
filemonitor-inotify.c	nomaintainer: Fix Lesser GPL version number	2020-11-15 17:04:40 +01:00
filemonitor-stub.c	nomaintainer: Fix Lesser GPL version number	2020-11-15 17:04:40 +01:00
getauxval.c	util/getauxval: Porting to FreeBSD getauxval feature	2020-06-26 06:45:29 -04:00
guest-random.c	replay: record and replay random number sources	2020-01-07 12:08:39 +01:00
hbitmap.c	block/dirty-bitmap: improve _next_dirty_area API	2020-03-18 14:03:46 -04:00
hexdump.c	util/hexdump: introduce qemu_hexdump_line()	2020-09-29 02:14:30 -04:00
host-utils.c	host-utils: Implement unsigned quadword left/right shift and unit tests	2017-01-31 10:10:14 +11:00
id.c	net: Use id_generate() in the network subsystem, too	2021-03-09 21:47:45 +01:00
iov.c	util/iov: make qemu_iovec_init_extended() honest	2021-02-03 08:00:33 -06:00
iova-tree.c	util: remove redundant include of glib.h and add osdep.h	2018-06-29 12:22:28 +01:00
keyval.c	keyval: Use GString to accumulate value strings	2020-12-19 10:39:23 +01:00
lockcnt.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
log.c	nomaintainer: Fix Lesser GPL version number	2020-11-15 17:04:40 +01:00
main-loop.c	qtest: delete superfluous inclusions of qtest.h	2021-03-09 06:03:53 +01:00
memfd.c	linux-user: add memfd_create	2019-09-11 08:46:17 +02:00
meson.build	migration: introduce UFFD-WP low-level interface helpers	2021-02-08 11:19:51 +00:00
mmap-alloc.c	memory: alloc RAM from file at offset	2021-02-09 20:53:56 +00:00
module.c	s390x: modularize virtio-gpu-ccw	2021-03-26 09:33:50 +01:00
notify.c	xen / notify: introduce a new XenWatchList abstraction	2019-09-24 12:18:47 +01:00
nvdimm-utils.c	Clean up includes	2020-12-10 17:16:44 +01:00
osdep.c	Pull request trivial patches 20200919	2020-09-22 15:42:23 +01:00
oslib-posix.c	memory: alloc RAM from file at offset	2021-02-09 20:53:56 +00:00
oslib-win32.c	util/oslib-win32: Fix _aligned_malloc() arguments order	2021-01-11 14:59:21 +01:00
pagesize.c	util: move qemu_real_host_page_size/mask to osdep.h	2017-10-10 09:45:00 -07:00
path.c	util/path: Do not cache all filenames at startup	2019-06-24 22:19:30 +02:00
qdist.c	qdist: return "(empty)" instead of NULL when printing an empty dist	2016-08-03 18:44:56 +02:00
qemu-co-shared-resource.c	util: introduce SharedResource	2019-10-28 11:22:31 +01:00
qemu-config.c	qemu-config: add error propagation to qemu_config_parse	2021-03-06 11:41:54 +01:00
qemu-coroutine-io.c	yield_until_fd_readable: make it work with any AioContect	2019-10-25 14:38:29 +02:00
qemu-coroutine-lock.c	coroutine-lock: Reimplement CoRwlock to fix downgrade bug	2021-03-31 10:44:21 +01:00
qemu-coroutine-sleep.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
qemu-coroutine.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
qemu-error.c	error: rename error_with_timestamp to message_with_timestamp	2021-02-01 10:50:55 +00:00
qemu-openpty.c	util/qemu-openpty.c: Don't assume pty.h is glibc-only	2020-07-13 14:36:09 +01:00
qemu-option.c	qemu-option: do not suggest using the delay option	2021-03-06 11:42:57 +01:00
qemu-print.c	monitor: Use getter/setter functions for cur_mon	2020-10-09 07:08:19 +02:00
qemu-progress.c	util/: fix some comment spelling errors	2020-09-17 20:38:42 +02:00
qemu-sockets.c	sockets: Make abstract UnixSocketAddress depend on CONFIG_LINUX	2020-11-03 13:17:25 +00:00
qemu-thread-common.h	Clean up includes	2018-12-20 10:29:08 +01:00
qemu-thread-posix.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
qemu-thread-win32.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
qemu-timer-common.c	semihosting: Implement SYS_ELAPSED and SYS_TICKFREQ	2021-01-18 10:05:06 +00:00
qemu-timer.c	ppc patch queue for 2021-03-10	2021-03-12 11:30:55 +00:00
qht.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
qsp.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
range.c	Don't talk about the LGPL if the file is licensed under the GPL	2019-01-30 10:51:20 +01:00
rcu.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
readline.c	readline: Fix possible array index out of bounds in readline_hist_add()	2021-01-04 11:13:39 +00:00
selfmap.c	linux-user: factor out reading of /proc/self/maps	2020-04-07 16:19:49 +01:00
stats64.c	qemu/atomic.h: rename atomic_ to qatomic_	2020-09-23 16:07:44 +01:00
sys_membarrier.c	sys_membarrier: fix up include directives	2018-04-05 14:37:38 +02:00
systemd.c	tools: Fix use of fcntl(F_SETFD) during socket activation	2020-05-04 14:54:35 -05:00
thread-pool.c	lockable: replaced locks with lock guard macros where appropriate	2020-05-04 16:07:43 +01:00
throttle.c	Remove superfluous timer_del() calls	2021-01-08 15:13:38 +00:00
timed-average.c	Fix some typos found by codespell	2016-05-18 15:04:27 +03:00
trace-events	migration: introduce UFFD-WP low-level interface helpers	2021-02-08 11:19:51 +00:00
trace.h	trace: switch position of headers to what Meson requires	2020-08-21 06:18:24 -04:00
unicode.c	json: Reject invalid UTF-8 sequences	2018-08-24 20:26:37 +02:00
uri.c	cutils: Provide strchrnul	2018-06-29 12:32:10 +02:00
userfaultfd.c	migration: introduce UFFD-WP low-level interface helpers	2021-02-08 11:19:51 +00:00
uuid.c	Include qemu-common.h exactly where needed	2019-06-12 13:20:20 +02:00
vfio-helpers.c	Pull request for 5.2	2020-11-23 13:03:13 +00:00
vhost-user-server.c	util/vhost-user-server: move header to include/	2020-10-23 13:42:16 +01:00
yank.c	Introduce yank feature	2021-01-13 10:21:17 +01:00