Commit Graph

30 Commits

Author SHA1 Message Date
Yury Kotov
3dcc9c6ec4 qemu-thread: Add qemu_cond_timedwait
The new function is needed to implement conditional sleep for CPU
throttling. It's possible to reuse qemu_sem_timedwait, but it's more
difficult than just add qemu_cond_timedwait.

Also moved compute_abs_deadline function up the code to reuse it in
qemu_cond_timedwait_impl win32.

Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>
Message-Id: <20190909131335.16848-2-yury-kotov@yandex-team.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-09-16 17:13:06 +02:00
Roman Bolshakov
21a43af0f1 qemu-thread: Don't block SEGV, ILL and FPE
If any of these signals happen on macOS, they are not delivered to other
threads and signalfd_compat receives nothing. Indeed, POSIX reference
and sigprocmask(2) note that an attempt to block the signals results in
undefined behaviour. SEGV and FPE can't also be received by signalfd(2)
on Linux.

An ability to retrieve SIGBUS via signalfd(2) is used by QEMU for
memory preallocation therefore we can't unblock it without consequences.
But it's important to leave a remark that the signal is lost on macOS.

Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2019-01-08 12:34:46 +00:00
Roman Bolshakov
479a57475e util: Implement debug-threads for macOS
macOS provides pthread_setname_np that doesn't have thread id argument.

Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2019-01-08 12:34:46 +00:00
Peter Maydell
a458774ad7 util/qemu-thread-posix: Fix qemu_thread_atexit* for OSX
Our current implementation of qemu_thread_atexit* is broken on OSX.
This is because it works by cerating a piece of thread-specific
data with pthread_key_create() and using the destructor function
for that data to run the notifier function passed to it by
the caller of qemu_thread_atexit_add(). The expected use case
is that the caller uses a __thread variable as the notifier,
and uses the callback to clean up information that it is
keeping per-thread in __thread variables.

Unfortunately, on OSX this does not work, because on OSX
a __thread variable may be destroyed (freed) before the
pthread_key_create() destructor runs. (POSIX imposes no
ordering constraint here; the OSX implementation happens
to implement __thread variables in terms of pthread_key_create((),
whereas Linux uses different mechanisms that mean the __thread
variables will still be present when the pthread_key_create()
destructor is run.)

Fix this by switching to a scheme similar to the one qemu-thread-win32
uses for qemu_thread_atexit: keep the thread's notifiers on a
__thread variable, and run the notifiers on calls to
qemu_thread_exit() and on return from the start routine passed
to qemu_thread_start(). We do this with the pthread_cleanup_push()
API.

We take advantage of the qemu_thread_atexit_add() API
permission not to run thread notifiers on process exit to
avoid having to special case the main thread.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181105135538.28025-3-peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-11-06 21:35:06 +01:00
Peter Xu
f1aff7aa8e qemu-thread: introduce qemu-thread-common.h
Introduce some hooks for the shared part of qemu thread between POSIX
and Windows implementations.  Note that in qemu_mutex_unlock_impl() we
moved the call before unlock operation which should make more sense.
And we don't need qemu_mutex_post_unlock() hook.

Put all these shared hooks into the header files.  It should be internal
to qemu-thread but not for qemu-thread users, hence put into util/
directory.

Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180425025459.5258-3-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-06-28 19:05:31 +02:00
Peter Xu
d820fa5b62 qemu-thread: always keep the posix wrapper layer
We will conditionally have a wrapper layer depending on whether the host
has the PTHREAD_SETNAME capability.  It complicates stuff.  Let's keep
the wrapper there; we opt out the pthread_setname_np() call only.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180412053444.17801-1-peterx@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-05-09 00:13:38 +02:00
Alex Bennée
6c27a0ded9 util/qemu-thread-*: add qemu_lock, locked and unlock trace events
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-01-16 14:54:52 +01:00
linzhecheng
68a9398261 qemu-thread: fix races on threads that exit very quickly
If we create a thread with QEMU_THREAD_DETACHED mode, QEMU may get a segfault with low probability.

The backtrace is:
     0x00007f46c60291d7 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
     0x00007f46c602a8c8 in __GI_abort () at abort.c:90
     0x00000000008543c9 in PAT_abort ()
     0x000000000085140d in patchIllInsHandler ()
     <signal handler called>
     pthread_detach (th=139933037614848) at pthread_detach.c:50
     0x0000000000829759 in qemu_thread_create (thread=thread@entry=0x7ffdaa8205e0, name=name@entry=0x94d94a "io-task-worker", start_routine=start_routine@entry=0x7eb9a0 <qio_task_thread_worker>,
       arg=arg@entry=0x3f5cf70, mode=mode@entry=1) at util/qemu_thread_posix.c:512
     0x00000000007ebc96 in qio_task_run_in_thread (task=0x31db2c0, worker=worker@entry=0x7e7e40 <qio_channel_socket_connect_worker>, opaque=0xcd23380, destroy=0x7f1180 <qapi_free_SocketAddress>)
       at io/task.c:141
     0x00000000007e7f33 in qio_channel_socket_connect_async (ioc=ioc@entry=0x626c0b0, addr=<optimized out>, callback=callback@entry=0x55e080 <qemu_chr_socket_connected>, opaque=opaque@entry=0x42862c0,
       destroy=destroy@entry=0x0) at io/channel_socket.c:194
     0x000000000055bdd1 in socket_reconnect_timeout (opaque=0x42862c0) at qemu_char.c:4744
    0x00007f46c72483b3 in g_timeout_dispatch () from /usr/lib64/libglib-2.0.so.0
    0x00007f46c724799a in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
    0x000000000076c646 in glib_pollfds_poll () at main_loop.c:228
    0x000000000076c6eb in os_host_main_loop_wait (timeout=348000000) at main_loop.c:273
    0x000000000076c815 in main_loop_wait (nonblocking=nonblocking@entry=0) at main_loop.c:521
    0x000000000056a511 in main_loop () at vl.c:2076
    0x0000000000420705 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4940

The cause of this problem is a glibc bug; for more information, see
https://sourceware.org/bugzilla/show_bug.cgi?id=19951.
The solution for this bug is to use pthread_attr_setdetachstate.

There is a similar issue with pthread_setname_np, which is moved
from creating thread to created thread.

Signed-off-by: linzhecheng <linzhecheng@huawei.com>
Message-Id: <20171128044656.10592-1-linzhecheng@huawei.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
[Simplify the code by removing qemu_thread_set_name, and free the arguments
 before invoking the start routine. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-12-20 22:29:26 +01:00
Peter Maydell
401bc051d7 util/qemu-thread-posix.c: Replace OS ifdefs with CONFIG_HAVE_SEM_TIMEDWAIT
In qemu-thread-posix.c we have two implementations of the
various qemu_sem_* functions, one of which uses native POSIX
sem_* and the other of which emulates them with pthread conditions.
This is necessary because not all our host OSes support
sem_timedwait().

Instead of a hard-coded list of OSes which don't implement
sem_timedwait(), which gets out of date, make configure
test for the presence of the function and set a new
CONFIG_HAVE_SEM_TIMEDWAIT appropriately.

In particular, newer NetBSDs have sem_timedwait(), so this
commit will switch them over to using it. OSX still does
not have an implementation.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Kamil Rytarowski <n54@gmx.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2017-09-26 09:06:02 +03:00
Fam Zheng
c096358e74 qemu-thread: Assert locks are initialized before using
Not all platforms check whether a lock is initialized before used.  In
particular Linux seems to be more permissive than OSX.

Check initialization state explicitly in our code to catch such bugs
earlier.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <20170704122325.25634-1-famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-07-04 14:39:28 +02:00
Jose Ricardo Ziviani
31f5a726b5 trace: add qemu mutex lock and unlock trace events
These trace events were very useful to help me to understand and find a
reordering issue in vfio, for example:

qemu_mutex_lock locked mutex 0x10905ad8
  vfio_region_write  (0001:03:00.0:region1+0xc0, 0x2020c, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
qemu_mutex_lock locked mutex 0x10905ad8
  vfio_region_write  (0001:03:00.0:region1+0xc4, 0xa0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8

that also helped me to see the desired result after the fix:

qemu_mutex_lock locked mutex 0x10905ad8
  vfio_region_write  (0001:03:00.0:region1+0xc0, 0x2000c, 4)
  vfio_region_write  (0001:03:00.0:region1+0xc4, 0xb0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8

So it could be a good idea to have these traces implemented. It's worth
mentioning that they should be surgically enabled during the debugging,
otherwise it can flood the trace logs with lock/unlock messages.

How to use it:
trace-event qemu_mutex_lock on|off
trace-event qemu_mutex_unlock on|off
or
trace-event qemu_mutex* on|off

Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
Message-Id: <1493054398-26013-1-git-send-email-joserz@linux.vnet.ibm.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
[Also handle trylock, cond_wait and win32; trace "unlocked" while still
 in the critical section, so that "unlocked" always comes before the
 next "locked" tracepoint. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-05-05 12:09:59 +02:00
Peter Maydell
598cf1c805 * QOM interface fix (Eduardo)
* RTC fixes (Gaohuai, Igor)
 * Memory leak fixes (Li Qiang, me)
 * Ctrl-a b regression (Marc-André)
 * Stubs cleanups and fixes (Leif, me)
 * hxtool tweak (me)
 * HAX support (Vincent)
 * QemuThread, exec.c and SCSI fixes (Roman, Xinhua, me)
 * PC_COMPAT_2_8 fix (Marcelo)
 * stronger bitmap assertions (Peter)
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Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

* QOM interface fix (Eduardo)
* RTC fixes (Gaohuai, Igor)
* Memory leak fixes (Li Qiang, me)
* Ctrl-a b regression (Marc-André)
* Stubs cleanups and fixes (Leif, me)
* hxtool tweak (me)
* HAX support (Vincent)
* QemuThread, exec.c and SCSI fixes (Roman, Xinhua, me)
* PC_COMPAT_2_8 fix (Marcelo)
* stronger bitmap assertions (Peter)

# gpg: Signature made Fri 20 Jan 2017 12:49:01 GMT
# gpg:                using RSA key 0xBFFBD25F78C7AE83
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>"
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>"
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini/tags/for-upstream: (35 commits)
  pc.h: move x-mach-use-reliable-get-clock compat entry to PC_COMPAT_2_8
  bitmap: assert that start and nr are non negative
  Revert "win32: don't run subprocess tests on Mingw32 platform"
  hax: add Darwin support
  Plumb the HAXM-based hardware acceleration support
  target/i386: Add Intel HAX files
  kvm: move cpu synchronization code
  KVM: PPC: eliminate unnecessary duplicate constants
  ramblock-notifier: new
  char: fix ctrl-a b not working
  exec: Add missing rcu_read_unlock
  x86: ioapic: fix fail migration when irqchip=split
  x86: ioapic: dump version for "info ioapic"
  x86: ioapic: add traces for ioapic
  hxtool: emit Texinfo headings as @subsection
  qemu-thread: fix qemu_thread_set_name() race in qemu_thread_create()
  serial: fix memory leak in serial exit
  scsi-block: fix direction of BYTCHK test for VERIFY commands
  pc: fix crash in rtc_set_memory() if initial cpu is marked as hotplugged
  acpi: filter based on CONFIG_ACPI_X86 rather than TARGET
  ...

# Conflicts:
#	include/hw/i386/pc.h
2017-01-20 16:42:07 +00:00
Caoxinhua
2f75bd73c3 qemu-thread: fix qemu_thread_set_name() race in qemu_thread_create()
QEMU will crash with the follow backtrace if the new created thread exited before
we call qemu_thread_set_name() for it.

  (gdb) bt
   0x00007f9a68b095d7 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
   0x00007f9a68b0acc8 in __GI_abort () at abort.c:90
   0x00007f9a69cda389 in PAT_abort () from /usr/lib64/libuvpuserhotfix.so
   0x00007f9a69cdda0d in patchIllInsHandler () from /usr/lib64/libuvpuserhotfix.so
   <signal handler called>
   pthread_setname_np (th=140298470549248, name=name@entry=0x8cc74a "io-task-worker") at ../nptl/sysdeps/unix/sysv/linux/pthread_setname.c:49
   0x00000000007f5f20 in qemu_thread_set_name (thread=thread@entry=0x7ffd2ac09680, name=name@entry=0x8cc74a "io-task-worker") at util/qemu_thread_posix.c:459
   0x00000000007f679e in qemu_thread_create (thread=thread@entry=0x7ffd2ac09680, name=name@entry=0x8cc74a "io-task-worker",start_routine=start_routine@entry=0x7c1300 <qio_task_thread_worker>, arg=arg@entry=0x7f99b8001720, mode=mode@entry=1) at util/qemu_thread_posix.c:498
   0x00000000007c15b6 in qio_task_run_in_thread (task=task@entry=0x7f99b80033d0, worker=worker@entry=0x7bd920 <qio_channel_socket_connect_worker>, opaque=0x7f99b8003370, destroy=0x7c6220 <qapi_free_SocketAddress>) at io/task.c:133
   0x00000000007bda04 in qio_channel_socket_connect_async (ioc=0x7f99b80014c0, addr=0x37235d0, callback=callback@entry=0x54ad00 <qemu_chr_socket_connected>, opaque=opaque@entry=0x38118b0, destroy=destroy@entry=0x0) at io/channel_socket.c:191
   0x00000000005487f6 in socket_reconnect_timeout (opaque=0x38118b0) at qemu_char.c:4402
   0x00007f9a6a1533b3 in g_timeout_dispatch () from /usr/lib64/libglib-2.0.so.0
   0x00007f9a6a15299a in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
   0x0000000000747386 in glib_pollfds_poll () at main_loop.c:227
   0x0000000000747424 in os_host_main_loop_wait (timeout=404000000) at main_loop.c:272
   0x0000000000747575 in main_loop_wait (nonblocking=nonblocking@entry=0) at main_loop.c:520
   0x0000000000557d31 in main_loop () at vl.c:2170
   0x000000000041c8b7 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:5083

Let's detach the new thread after calling qemu_thread_set_name().

Signed-off-by: Caoxinhua <caoxinhua@huawei.com>
Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Message-Id: <1483493521-9604-1-git-send-email-zhang.zhanghailiang@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-01-16 17:52:35 +01:00
Paolo Bonzini
fbcc3e5004 qemu-thread: optimize QemuLockCnt with futexes on Linux
This is complex, but I think it is reasonably documented in the source.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170112180800.21085-5-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-16 13:25:18 +00:00
Paolo Bonzini
feadec6384 qemu-thread: introduce QemuRecMutex
GRecMutex is new in glib 2.32, so we cannot use it.  Introduce
a recursive mutex in qemu-thread instead, which will be used
instead of RFifoLock.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1477565348-5458-20-git-send-email-pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
2016-10-28 21:50:18 +08:00
Paolo Bonzini
374293ca6f qemu-thread: use acquire/release to clarify semantics of QemuEvent
Do not use the somewhat mysterious atomic_mb_read/atomic_mb_set,
instead make sure that the operations on QemuEvent are annotated
with the desired acquire and release semantics.

In particular, qemu_event_set wakes up the waiting thread, so it must
be a release from the POV of the waker (compare with qemu_mutex_unlock).
And it actually needs a full barrier, because that's the only thing that
provides something like a "load-release".

Use smp_mb_acquire until we have atomic_load_acquire and
atomic_store_release in atomic.h.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-10-24 11:30:55 +02:00
Peter Maydell
aafd758410 util: Clean up includes
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.

This commit was created with scripts/clean-includes.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1454089805-5470-6-git-send-email-peter.maydell@linaro.org
2016-02-04 17:01:04 +00:00
Peter Maydell
a2aa09e181 * Support for jemalloc
* qemu_mutex_lock_iothread "No such process" fix
 * cutils: qemu_strto* wrappers
 * iohandler.c simplification
 * Many other fixes and misc patches.
 
 And some MTTCG work (with Emilio's fixes squashed):
 * Signal-free TCG kick
 * Removing spinlock in favor of QemuMutex
 * User-mode emulation multi-threading fixes/docs
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Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

* Support for jemalloc
* qemu_mutex_lock_iothread "No such process" fix
* cutils: qemu_strto* wrappers
* iohandler.c simplification
* Many other fixes and misc patches.

And some MTTCG work (with Emilio's fixes squashed):
* Signal-free TCG kick
* Removing spinlock in favor of QemuMutex
* User-mode emulation multi-threading fixes/docs

# gpg: Signature made Thu 10 Sep 2015 09:03:07 BST using RSA key ID 78C7AE83
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>"
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>"

* remotes/bonzini/tags/for-upstream: (44 commits)
  cutils: work around platform differences in strto{l,ul,ll,ull}
  cpu-exec: fix lock hierarchy for user-mode emulation
  exec: make mmap_lock/mmap_unlock globally available
  tcg: comment on which functions have to be called with mmap_lock held
  tcg: add memory barriers in page_find_alloc accesses
  remove unused spinlock.
  replace spinlock by QemuMutex.
  cpus: remove tcg_halt_cond and tcg_cpu_thread globals
  cpus: protect work list with work_mutex
  scripts/dump-guest-memory.py: fix after RAMBlock change
  configure: Add support for jemalloc
  add macro file for coccinelle
  configure: factor out adding disas configure
  vhost-scsi: fix wrong vhost-scsi firmware path
  checkpatch: remove tests that are not relevant outside the kernel
  checkpatch: adapt some tests to QEMU
  CODING_STYLE: update mixed declaration rules
  qmp: Add example usage of strto*l() qemu wrapper
  cutils: Add qemu_strtoull() wrapper
  cutils: Add qemu_strtoll() wrapper
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2015-09-14 16:13:16 +01:00
Veres Lajos
67cc32ebfd typofixes - v4
Signed-off-by: Veres Lajos <vlajos@gmail.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2015-09-11 10:45:43 +03:00
Emilio G. Cota
16ef9d0252 qemu-thread: handle spurious futex_wait wakeups
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1440375847-17603-12-git-send-email-cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-09-02 23:03:03 +02:00
Paolo Bonzini
24fa90499f qemu-thread: do not use PTHREAD_MUTEX_ERRORCHECK
PTHREAD_MUTEX_ERRORCHECK is completely broken with respect to fork.
The way to safely do fork is to bring all threads to a quiescent
state by acquiring locks (either in callers---as we do for the
iothread mutex---or using pthread_atfork's prepare callbacks)
and then release them in the child.

The problem is that releasing error-checking locks in the child
fails under glibc with EPERM, because the mutex stores a different
owner tid than the duplicated thread in the child process.  We
could make it work for locks acquired via pthread_atfork, by
recreating the mutex in the child instead of unlocking it
(we know that there are no other threads that could have taken
the mutex; but when the lock is acquired in fork's caller
that would not be possible.

The simplest solution is just to forgo error checking.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-03-10 10:49:25 +01:00
Paolo Bonzini
158ef8cbb7 qemu-thread: fix qemu_event without futexes
This had a possible deadlock that was visible with rcutorture.

    qemu_event_set                    qemu_event_wait
    ----------------------------------------------------------------
                                      cmpxchg reads FREE, writes BUSY
                                      futex_wait: pthread_mutex_lock
                                      futex_wait: value == BUSY
    xchg reads BUSY, writes SET
    futex_wake: pthread_cond_broadcast
                                      futex_wait: pthread_cond_wait
                                      <deadlock>

The fix is simply to avoid condvar tricks and do the obvious locking
around pthread_cond_broadcast:

    qemu_event_set        qemu_event_wait
    ----------------------------------------------------------------
                                      cmpxchg reads FREE, writes BUSY
                                      futex_wait: pthread_mutex_lock
                                      futex_wait: value == BUSY
    xchg reads BUSY, writes SET
    futex_wake: pthread_mutex_lock
    (blocks)
                                      futex_wait: pthread_cond_wait
    (mutex unlocked)
    futex_wake: pthread_cond_broadcast
    futex_wake: pthread_mutex_unlock
                                      futex_wait: pthread_mutex_unlock

Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-02-02 16:55:09 +01:00
Paolo Bonzini
ef57137f1b qemu-thread: add per-thread atexit functions
Destructors are the main additional feature of pthread TLS compared
to __thread.  If we were using C++ (hint, hint!) we could have used
thread-local objects with a destructor.  Since we are not, instead,
we add a simple Notifier-based API.

Note that the notifier must be per-thread as well.  We can add a
global list as well later, perhaps.

The Win32 implementation has some complications because a) detached
threads used not to have a QemuThreadData; b) the main thread does
not go through win32_start_routine, so we have to use atexit too.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1417518350-6167-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-01-13 13:43:29 +00:00
Dr. David Alan Gilbert
5c31207941 Detect pthread_setname_np at configure time
Warn if no way of setting thread name is available.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2014-03-27 17:48:11 +02:00
Jan Kiszka
01207d0b78 qemu-thread-posix: Fix build against older glibc version
pthread_setname_np was introduced with 2.12.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2014-03-11 18:19:21 +00:00
Dr. David Alan Gilbert
4900116e6f Add a 'name' parameter to qemu_thread_create
If enabled, set the thread name at creation (on GNU systems with
  pthread_set_np)
Fix up all the callers with a thread name

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
2014-03-09 21:09:38 +02:00
Dr. David Alan Gilbert
8f480de0c9 Add 'debug-threads' suboption to --name
Add flag storage to qemu-thread-* to store the namethreads flag

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
2014-03-09 21:09:37 +02:00
Paolo Bonzini
c7c4d063f5 qemu-thread: add QemuEvent
This emulates Win32 manual-reset events using futexes or conditional
variables.  Typical ways to use them are with multi-producer,
single-consumer data structures, to test for a complex condition whose
elements come from different threads:

    for (;;) {
        qemu_event_reset(ev);
        ... test complex condition ...
        if (condition is true) {
            break;
        }
        qemu_event_wait(ev);
    }

Or more efficiently (but with some duplication):

    ... evaluate condition ...
    while (!condition) {
        qemu_event_reset(ev);
        ... evaluate condition ...
        if (!condition) {
            qemu_event_wait(ev);
            ... evaluate condition ...
        }
    }

QemuEvent provides a very fast userspace path in the common case when
no other thread is waiting, or the event is not changing state.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2013-10-17 17:30:55 +02:00
Izumi Tsutsui
79761c6681 semaphore: fix a hangup problem under load on NetBSD hosts.
Fix following bugs in "fallback implementation of counting semaphores
with mutex+condvar" added in c166cb72f1:
 - waiting threads are not restarted properly if more than one threads
   are waiting unblock signals in qemu_sem_timedwait()
 - possible missing pthread_cond_signal(3) calls when waiting threads
   are returned by ETIMEDOUT
 - fix an uninitialized variable
The problem is analyzed by and fix is provided by Noriyuki Soda.

Also put additional cleanup suggested by Laszlo Ersek:
 - make QemuSemaphore.count unsigned (it won't be negative)
 - check a return value of in pthread_cond_wait() in qemu_sem_wait()

Signed-off-by: Izumi Tsutsui <tsutsui@ceres.dti.ne.jp>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1372841894-10634-1-git-send-email-tsutsui@ceres.dti.ne.jp
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2013-08-05 11:48:00 -05:00
Paolo Bonzini
baacf04799 build: move libqemuutil.a components to util/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2013-01-12 18:42:50 +01:00