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[Qemu-devel] [PULL 12/15] cpus: don't use atomic_read for vm_clock_warp_
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 12/15] cpus: don't use atomic_read for vm_clock_warp_start |
Date: |
Tue, 5 Apr 2016 11:50:15 +0200 |
From: Alex Bennée <address@hidden>
As vm_clock_warp_start is a 64 bit value this causes problems for the
compiler trying to come up with a suitable atomic operation on 32 bit
hosts. Because the variable is protected by vm_clock_seqlock, we check its
value inside a seqlock critical section.
Signed-off-by: Alex Bennée <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
cpus.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/cpus.c b/cpus.c
index 8ae4777..cbeb1f6 100644
--- a/cpus.c
+++ b/cpus.c
@@ -338,10 +338,18 @@ static int64_t qemu_icount_round(int64_t count)
static void icount_warp_rt(void)
{
+ unsigned seq;
+ int64_t warp_start;
+
/* The icount_warp_timer is rescheduled soon after vm_clock_warp_start
* changes from -1 to another value, so the race here is okay.
*/
- if (atomic_read(&vm_clock_warp_start) == -1) {
+ do {
+ seq = seqlock_read_begin(&timers_state.vm_clock_seqlock);
+ warp_start = vm_clock_warp_start;
+ } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, seq));
+
+ if (warp_start == -1) {
return;
}
--
2.5.5
- [Qemu-devel] [PULL 05/15] target-i386: assert that KVM_GET/SET_MSRS can set all requested MSRs, (continued)
- [Qemu-devel] [PULL 05/15] target-i386: assert that KVM_GET/SET_MSRS can set all requested MSRs, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 09/15] char: ensure all clients are in non-blocking mode, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 08/15] char: fix broken EAGAIN retry on OS-X due to errno clobbering, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 10/15] doc/memory: update MMIO section, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 07/15] util: retry getaddrinfo if getting EAI_BADFLAGS with AI_V4MAPPED, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 11/15] nbd: don't request FUA on FLUSH, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 06/15] checkpatch: add target_ulong to typelist, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 14/15] nbd: Fix poor debug message, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 12/15] cpus: don't use atomic_read for vm_clock_warp_start,
Paolo Bonzini <=
- [Qemu-devel] [PULL 13/15] include/qemu/atomic: add compile time asserts, Paolo Bonzini, 2016/04/05
- [Qemu-devel] [PULL 15/15] net: fix missing include of qapi/error.h in netmap.c, Paolo Bonzini, 2016/04/05
- Re: [Qemu-devel] [PULL 00/15] Misc changes for QEMU 2.6.0-rc1, Peter Maydell, 2016/04/05