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Fix race condition on access to env->interrupt_request

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env->interrupt_request is accessed as the bit level from both main code
and signal handler, making a race condition possible even on CISC CPU.
This causes freeze of QEMU under high load when running the dyntick
clock.

The patch below move the bit corresponding to CPU_INTERRUPT_EXIT in a
separate variable, declared as volatile sig_atomic_t, so it should be
work even on RISC CPU.

We may want to move the cpu_interrupt(env, CPU_INTERRUPT_EXIT) case in
its own function and get rid of CPU_INTERRUPT_EXIT. That can be done
later, I wanted to keep the patch short for easier review.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6728 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
aurel32 2009-03-06 21:48:00 +00:00
parent 28a76be8f4
commit be214e6c05
4 changed files with 19 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

11
exec.c
View file

@ -1501,9 +1501,12 @@ void cpu_interrupt(CPUState *env, int mask)
#endif
int old_mask;
if (mask & CPU_INTERRUPT_EXIT) {
env->exit_request = 1;
mask &= ~CPU_INTERRUPT_EXIT;
}
old_mask = env->interrupt_request;
/* FIXME: This is probably not threadsafe. A different thread could
be in the middle of a read-modify-write operation. */
env->interrupt_request |= mask;
#if defined(USE_NPTL)
/* FIXME: TB unchaining isn't SMP safe. For now just ignore the
@ -1514,10 +1517,8 @@ void cpu_interrupt(CPUState *env, int mask)
if (use_icount) {
env->icount_decr.u16.high = 0xffff;
#ifndef CONFIG_USER_ONLY
/* CPU_INTERRUPT_EXIT isn't a real interrupt. It just means
an async event happened and we need to process it. */
if (!can_do_io(env)
&& (mask & ~(old_mask | CPU_INTERRUPT_EXIT)) != 0) {
&& (mask & ~old_mask) != 0) {
cpu_abort(env, "Raised interrupt while not in I/O function");
}
#endif