From 426eeecdf5d9cf1695a53c08f46394f8e5351750 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 2 Nov 2017 16:35:36 +0000 Subject: cpu-exec: Exit exclusive region on longjmp from step_atomic MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Commit ac03ee5331612e44be narrowed the scope of the exclusive region so it only covers when we're executing the TB, not when we're generating it. However it missed that there is more than one execution path out of cpu_tb_exec -- if the atomic insn causes an exception then the code will longjmp out, skipping the code to end the exclusive region. This causes QEMU to hang the next time the CPU calls start_exclusive(), waiting for itself to exit the region. Move the "end the region" code out to the end of the function so that it is run for both normal exit and also for exit-via-longjmp. We have to use a volatile bool flag to decide whether we need to end the region, because we can longjump out of the codegen as well as the execution. (For some reason this only reproduces for me with a clang optimized build, not a gcc debug build.) Reviewed-by: Emilio G. Cota Reviewed-by: Alex Bennée Reviewed-by: Richard Henderson Fixes: ac03ee5331612e44beb393df2b578c951d27dc0d Signed-off-by: Peter Maydell Message-Id: <1509640536-32160-1-git-send-email-peter.maydell@linaro.org> Signed-off-by: Richard Henderson --- accel/tcg/cpu-exec.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) (limited to 'accel/tcg') diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 4318441e4c..61297f8f4a 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -233,6 +233,8 @@ void cpu_exec_step_atomic(CPUState *cpu) uint32_t flags; uint32_t cflags = 1; uint32_t cf_mask = cflags & CF_HASH_MASK; + /* volatile because we modify it between setjmp and longjmp */ + volatile bool in_exclusive_region = false; if (sigsetjmp(cpu->jmp_env, 0) == 0) { tb = tb_lookup__cpu_state(cpu, &pc, &cs_base, &flags, cf_mask); @@ -251,14 +253,12 @@ void cpu_exec_step_atomic(CPUState *cpu) /* Since we got here, we know that parallel_cpus must be true. */ parallel_cpus = false; + in_exclusive_region = true; cc->cpu_exec_enter(cpu); /* execute the generated code */ trace_exec_tb(tb, pc); cpu_tb_exec(cpu, tb); cc->cpu_exec_exit(cpu); - parallel_cpus = true; - - end_exclusive(); } else { /* We may have exited due to another problem here, so we need * to reset any tb_locks we may have taken but didn't release. @@ -270,6 +270,15 @@ void cpu_exec_step_atomic(CPUState *cpu) #endif tb_lock_reset(); } + + if (in_exclusive_region) { + /* We might longjump out of either the codegen or the + * execution, so must make sure we only end the exclusive + * region if we started it. + */ + parallel_cpus = true; + end_exclusive(); + } } struct tb_desc { -- cgit v1.2.1