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authorPeter Maydell <peter.maydell@linaro.org>2013-02-22 18:10:03 +0000
committerBlue Swirl <blauwirbel@gmail.com>2013-03-03 14:28:47 +0000
commit378df4b23753a11be650af7664ca76bc75cb9f01 (patch)
treecedcd8fd2c8b23401ca4275ce65388e745cbcb37 /cpu-exec.c
parent77211379d73ea0c89c0b5bb6eee74b17cb06f9a8 (diff)
downloadqemu-arm-378df4b23753a11be650af7664ca76bc75cb9f01.tar.gz
Handle CPU interrupts by inline checking of a flag
Fix some of the nasty TCG race conditions and crashes by implementing cpu_exit() as setting a flag which is checked at the start of each TB. This avoids crashes if a thread or signal handler calls cpu_exit() while the execution thread is itself modifying the TB graph (which may happen in system emulation mode as well as in linux-user mode with a multithreaded guest binary). This fixes the crashes seen in LP:668799; however there are another class of crashes described in LP:1098729 which stem from the fact that in linux-user with a multithreaded guest all threads will use and modify the same global TCG date structures (including the generated code buffer) without any kind of locking. This means that multithreaded guest binaries are still in the "unsupported" category. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Diffstat (limited to 'cpu-exec.c')
-rw-r--r--cpu-exec.c25
1 files changed, 24 insertions, 1 deletions
diff --git a/cpu-exec.c b/cpu-exec.c
index f9ea080e31..9092145d0b 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -64,6 +64,12 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, uint8_t *tb_ptr)
TranslationBlock *tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
cpu_pc_from_tb(env, tb);
}
+ if ((next_tb & TB_EXIT_MASK) == TB_EXIT_REQUESTED) {
+ /* We were asked to stop executing TBs (probably a pending
+ * interrupt. We've now stopped, so clear the flag.
+ */
+ cpu->tcg_exit_req = 0;
+ }
return next_tb;
}
@@ -608,7 +614,20 @@ int cpu_exec(CPUArchState *env)
tc_ptr = tb->tc_ptr;
/* execute the generated code */
next_tb = cpu_tb_exec(cpu, tc_ptr);
- if ((next_tb & TB_EXIT_MASK) == TB_EXIT_ICOUNT_EXPIRED) {
+ switch (next_tb & TB_EXIT_MASK) {
+ case TB_EXIT_REQUESTED:
+ /* Something asked us to stop executing
+ * chained TBs; just continue round the main
+ * loop. Whatever requested the exit will also
+ * have set something else (eg exit_request or
+ * interrupt_request) which we will handle
+ * next time around the loop.
+ */
+ tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
+ next_tb = 0;
+ break;
+ case TB_EXIT_ICOUNT_EXPIRED:
+ {
/* Instruction counter expired. */
int insns_left;
tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
@@ -632,6 +651,10 @@ int cpu_exec(CPUArchState *env)
next_tb = 0;
cpu_loop_exit(env);
}
+ break;
+ }
+ default:
+ break;
}
}
cpu->current_tb = NULL;