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[Qemu-devel] [Bug 1817865] Re: sorecvfrom freezes guest
From: |
Vic |
Subject: |
[Qemu-devel] [Bug 1817865] Re: sorecvfrom freezes guest |
Date: |
Thu, 28 Feb 2019 10:55:47 -0000 |
Found out that the guest freeze issue is due to a block udp reading call
rather than a deaklock. I have rephase the bug description and sent a
patch in qemu-devel.
** Summary changed:
- deadlock in prepare_mmio_access reading mmio
+ sorecvfrom freezes guest
** Description changed:
QEMU release 3.1.0; Guest running win10.
- The deadlock happens in prepare_mmio_access call when the guest is
- trying to read MMIO address 0xFEBC00C0. This address belongs to
- "Intel(R) PRO/1000 MT Network Connection" as shown in Windows 10 device
- manager. A quick analysis has shown that in prepare_mmio_access call:
-
- static bool prepare_mmio_access(MemoryRegion *mr)
- {
- bool unlocked = !qemu_mutex_iothread_locked();
- bool release_lock = false;
-
- if (unlocked && mr->global_locking) {
- qemu_mutex_lock_iothread();
- ...
-
- "qemu_mutex_iothread_locked()" and "qemu_mutex_lock_iothread()" are not
- atomic operation, so the global mutex could become locked by "util/main-
- loop.c" (line = 236) after "qemu_mutex_iothread_locked()" is called.
-
- GDB backtrace analysis as following:
-
- (gdb) thread 9
- [Switching to thread 9 (Thread 0x7fffe6b7c700 (LWP 14405))]
- #0 __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:103
- 103 ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S: No such file or
directory.
- (gdb) bt
- #0 __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:103
- #1 0x00007ffff748c714 in __GI___pthread_mutex_lock (mutex=0x555556518340
<qemu_global_mutex>) at ../nptl/pthread_mutex_lock.c:80
- #2 0x0000555555d8ae7b in qemu_mutex_lock_impl (mutex=0x555556518340
<qemu_global_mutex>,
- file=0x555555e7a298 "/home/vic/Projects/tc-qemu/exec.c", line=3197) at
util/qemu-thread-posix.c:66
- #3 0x000055555584cf66 in qemu_mutex_lock_iothread_impl (file=0x555555e7a298
"/home/vic/Projects/tc-qemu/exec.c", line=3197)
- at /home/vic/Projects/tc-qemu/cpus.c:1849
- #4 0x0000555555804ccc in prepare_mmio_access (mr=0x5555575b9000) at
/home/vic/Projects/tc-qemu/exec.c:3197
- #5 0x0000555555804f90 in flatview_read_continue (fv=0x7fffd86f2390,
addr=4273733824, attrs=..., buf=0x7ffff7fcc028 "ۜ/o", len=4,
- addr1=192, l=4, mr=0x5555575b9000) at
/home/vic/Projects/tc-qemu/exec.c:3292
- #6 0x0000555555805136 in flatview_read (fv=0x7fffd86f2390, addr=4273733824,
attrs=..., buf=0x7ffff7fcc028 "ۜ/o", len=4)
- at /home/vic/Projects/tc-qemu/exec.c:3332
- #7 0x00005555558051aa in address_space_read_full (as=0x555556517bc0
<address_space_memory>, addr=4273733824, attrs=...,
- buf=0x7ffff7fcc028 "ۜ/o", len=4) at /home/vic/Projects/tc-qemu/exec.c:3345
- #8 0x0000555555805281 in address_space_rw (as=0x555556517bc0
<address_space_memory>, addr=4273733824, attrs=...,
- buf=0x7ffff7fcc028 "ۜ/o", len=4, is_write=false) at
/home/vic/Projects/tc-qemu/exec.c:3375
- #9 0x0000555555886199 in kvm_cpu_exec (cpu=0x5555566d1800) at
/home/vic/Projects/tc-qemu/accel/kvm/kvm-all.c:2031
- #10 0x000055555584c001 in qemu_kvm_cpu_thread_fn (arg=0x5555566d1800) at
/home/vic/Projects/tc-qemu/cpus.c:1281
- #11 0x0000555555d8b9f7 in qemu_thread_start (args=0x5555566f3c00) at
util/qemu-thread-posix.c:498
- #12 0x00007ffff7489fa3 in start_thread (arg=<optimized out>) at
pthread_create.c:486
- #13 0x00007ffff73ba80f in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
- (gdb) f 2
- #2 0x0000555555d8ae7b in qemu_mutex_lock_impl (mutex=0x555556518340
<qemu_global_mutex>,
- file=0x555555e7a298 "/home/vic/Projects/tc-qemu/exec.c", line=3197) at
util/qemu-thread-posix.c:66
- 66 err = pthread_mutex_lock(&mutex->lock);
- (gdb) p mutex
- $1 = (QemuMutex *) 0x555556518340 <qemu_global_mutex>
- (gdb) p *mutex
- $2 = {lock = pthread_mutex_t = {Type = Normal, Status = Acquired, possibly
with waiters, Owner ID = 14393, Robust = No, Shared = No,
- Protocol = None}, file = 0x555555fc2a64 "util/main-loop.c", line = 236,
initialized = true}
- (gdb) thread 1
- [Switching to thread 1 (Thread 0x7ffff495cc00 (LWP 14393))]
- #0 0x00007ffff7493832 in __libc_recvfrom (fd=147, buf=0x7fffd81ce0cc,
len=1500, flags=0, addr=..., addrlen=0x7fffffffd9a8)
- at ../sysdeps/unix/sysv/linux/recvfrom.c:27
- 27 ../sysdeps/unix/sysv/linux/recvfrom.c: No such file or directory.
- (gdb) bt
- #0 0x00007ffff7493832 in __libc_recvfrom (fd=147, buf=0x7fffd81ce0cc,
len=1500, flags=0, addr=..., addrlen=0x7fffffffd9a8)
- at ../sysdeps/unix/sysv/linux/recvfrom.c:27
- #1 0x0000555555c18bf3 in sorecvfrom (so=0x7fffd818fe60) at slirp/socket.c:584
- #2 0x0000555555c146f9 in slirp_pollfds_poll (pollfds=0x555556655470,
select_error=0) at slirp/slirp.c:753
- #3 0x0000555555d8675b in main_loop_wait (nonblocking=0) at
util/main-loop.c:498
- #4 0x00005555559d2194 in main_loop () at vl.c:1893
- #5 0x00005555559d9d93 in main (argc=16, argv=0x7fffffffdff8,
envp=0x7fffffffe080) at vl.c:4692
+ Sometimes sorecvfrom() is called from slirp.c because revents ==
+ G_IO_IN, however inside sorecvfrom() function, ioctlsocket() returns 0
+ bytes available and recvfrom could be blocking indefinitely.
--
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https://bugs.launchpad.net/bugs/1817865
Title:
sorecvfrom freezes guest
Status in QEMU:
New
Bug description:
QEMU release 3.1.0; Guest running win10.
Sometimes sorecvfrom() is called from slirp.c because revents ==
G_IO_IN, however inside sorecvfrom() function, ioctlsocket() returns 0
bytes available and recvfrom could be blocking indefinitely.
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