gwj / at91sam9263 · Commits

Commit be214e6c0557139ffa5551f77e339c07495bfec3

Authored by aurel32
1 parent 28a76be8

Fix race condition on access to env->interrupt_request 

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
Inline Side-by-side
Showing 4 changed files with 19 additions and 16 deletions
cpu-defs.h
  View file @be214e6
... ... @@ -27,6 +27,7 @@
27 27 #include "config.h"
28 28 #include <setjmp.h>
29 29 #include <inttypes.h>
  30 +#include <signal.h>
30 31 #include "osdep.h"
31 32 #include "sys-queue.h"
32 33  
... ... @@ -170,6 +171,7 @@ typedef struct CPUWatchpoint {
170 171 memory was accessed */ \
171 172 uint32_t halted; /* Nonzero if the CPU is in suspend state */ \
172 173 uint32_t interrupt_request; \
  174 + volatile sig_atomic_t exit_request; \
173 175 /* The meaning of the MMU modes is defined in the target code. */ \
174 176 CPUTLBEntry tlb_table[NB_MMU_MODES][CPU_TLB_SIZE]; \
175 177 target_phys_addr_t iotlb[NB_MMU_MODES][CPU_TLB_SIZE]; \
... ...
cpu-exec.c
  View file @be214e6
... ... @@ -311,7 +311,7 @@ int cpu_exec(CPUState *env1)
311 311 env->exception_index = -1;
312 312 }
313 313 #ifdef USE_KQEMU
314   - if (kqemu_is_ok(env) && env->interrupt_request == 0) {
  314 + if (kqemu_is_ok(env) && env->interrupt_request == 0 && env->exit_request == 0) {
315 315 int ret;
316 316 env->eflags = env->eflags | helper_cc_compute_all(CC_OP) | (DF & DF_MASK);
317 317 ret = kqemu_cpu_exec(env);
... ... @@ -326,7 +326,7 @@ int cpu_exec(CPUState *env1)
326 326 } else if (ret == 2) {
327 327 /* softmmu execution needed */
328 328 } else {
329   - if (env->interrupt_request != 0) {
  329 + if (env->interrupt_request != 0 || env->exit_request != 0) {
330 330 /* hardware interrupt will be executed just after */
331 331 } else {
332 332 /* otherwise, we restart */
... ... @@ -525,11 +525,11 @@ int cpu_exec(CPUState *env1)
525 525 the program flow was changed */
526 526 next_tb = 0;
527 527 }
528   - if (interrupt_request & CPU_INTERRUPT_EXIT) {
529   - env->interrupt_request &= ~CPU_INTERRUPT_EXIT;
530   - env->exception_index = EXCP_INTERRUPT;
531   - cpu_loop_exit();
532   - }
  528 + }
  529 + if (unlikely(env->exit_request)) {
  530 + env->exit_request = 0;
  531 + env->exception_index = EXCP_INTERRUPT;
  532 + cpu_loop_exit();
533 533 }
534 534 #ifdef DEBUG_EXEC
535 535 if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {
... ... @@ -599,7 +599,7 @@ int cpu_exec(CPUState *env1)
599 599 TB, but before it is linked into a potentially
600 600 infinite loop and becomes env->current_tb. Avoid
601 601 starting execution if there is a pending interrupt. */
602   - if (unlikely (env->interrupt_request & CPU_INTERRUPT_EXIT))
  602 + if (unlikely (env->exit_request))
603 603 env->current_tb = NULL;
604 604  
605 605 while (env->current_tb) {
... ...
... ... @@ -1501,9 +1501,12 @@ void cpu_interrupt(CPUState *env, int mask)
1501 1501 #endif
1502 1502 int old_mask;
1503 1503  
  1504 + if (mask & CPU_INTERRUPT_EXIT) {
  1505 + env->exit_request = 1;
  1506 + mask &= ~CPU_INTERRUPT_EXIT;
  1507 + }
  1508 +
1504 1509 old_mask = env->interrupt_request;
1505   - /* FIXME: This is probably not threadsafe. A different thread could
1506   - be in the middle of a read-modify-write operation. */
1507 1510 env->interrupt_request |= mask;
1508 1511 #if defined(USE_NPTL)
1509 1512 /* FIXME: TB unchaining isn't SMP safe. For now just ignore the
... ... @@ -1514,10 +1517,8 @@ void cpu_interrupt(CPUState *env, int mask)
1514 1517 if (use_icount) {
1515 1518 env->icount_decr.u16.high = 0xffff;
1516 1519 #ifndef CONFIG_USER_ONLY
1517   - /* CPU_INTERRUPT_EXIT isn't a real interrupt. It just means
1518   - an async event happened and we need to process it. */
1519 1520 if (!can_do_io(env)
1520   - && (mask & ~(old_mask | CPU_INTERRUPT_EXIT)) != 0) {
  1521 + && (mask & ~old_mask) != 0) {
1521 1522 cpu_abort(env, "Raised interrupt while not in I/O function");
1522 1523 }
1523 1524 #endif
... ...
kvm-all.c
  View file @be214e6
... ... @@ -445,7 +445,7 @@ int kvm_cpu_exec(CPUState *env)
445 445 do {
446 446 kvm_arch_pre_run(env, run);
447 447  
448   - if ((env->interrupt_request & CPU_INTERRUPT_EXIT)) {
  448 + if (env->exit_request) {
449 449 dprintf("interrupt exit requested\n");
450 450 ret = 0;
451 451 break;
... ... @@ -512,8 +512,8 @@ int kvm_cpu_exec(CPUState *env)
512 512 }
513 513 } while (ret > 0);
514 514  
515   - if ((env->interrupt_request & CPU_INTERRUPT_EXIT)) {
516   - env->interrupt_request &= ~CPU_INTERRUPT_EXIT;
  515 + if (env->exit_request) {
  516 + env->exit_request = 0;
517 517 env->exception_index = EXCP_INTERRUPT;
518 518 }
519 519  
... ...