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[Qemu-devel] [PULL 20/39] tcg: Clarify thread safety check in tb_add_jum
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PULL 20/39] tcg: Clarify thread safety check in tb_add_jump() |
Date: |
Thu, 12 May 2016 14:13:21 -1000 |
From: Sergey Fedorov <address@hidden>
The check is to make sure that another thread hasn't already done the
same while we were outside of tb_lock. Mention this in a comment.
Signed-off-by: Sergey Fedorov <address@hidden>
Signed-off-by: Sergey Fedorov <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
---
include/exec/exec-all.h | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 64c2a66..06da1bc 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -372,20 +372,23 @@ static inline void tb_set_jmp_target(TranslationBlock *tb,
static inline void tb_add_jump(TranslationBlock *tb, int n,
TranslationBlock *tb_next)
{
- /* NOTE: this test is only needed for thread safety */
- if (!tb->jmp_list_next[n]) {
- qemu_log_mask_and_addr(CPU_LOG_EXEC, tb->pc,
- "Linking TBs %p [" TARGET_FMT_lx
- "] index %d -> %p [" TARGET_FMT_lx "]\n",
- tb->tc_ptr, tb->pc, n,
- tb_next->tc_ptr, tb_next->pc);
- /* patch the native jump address */
- tb_set_jmp_target(tb, n, (uintptr_t)tb_next->tc_ptr);
-
- /* add in TB jmp circular list */
- tb->jmp_list_next[n] = tb_next->jmp_list_first;
- tb_next->jmp_list_first = (uintptr_t)tb | n;
+ if (tb->jmp_list_next[n]) {
+ /* Another thread has already done this while we were
+ * outside of the lock; nothing to do in this case */
+ return;
}
+ qemu_log_mask_and_addr(CPU_LOG_EXEC, tb->pc,
+ "Linking TBs %p [" TARGET_FMT_lx
+ "] index %d -> %p [" TARGET_FMT_lx "]\n",
+ tb->tc_ptr, tb->pc, n,
+ tb_next->tc_ptr, tb_next->pc);
+
+ /* patch the native jump address */
+ tb_set_jmp_target(tb, n, (uintptr_t)tb_next->tc_ptr);
+
+ /* add in TB jmp circular list */
+ tb->jmp_list_next[n] = tb_next->jmp_list_first;
+ tb_next->jmp_list_first = (uintptr_t)tb | n;
}
/* GETRA is the true target of the return instruction that we'll execute,
--
2.5.5
- [Qemu-devel] [PULL 11/39] tcg/mips: Make direct jump patching thread-safe, (continued)
- [Qemu-devel] [PULL 11/39] tcg/mips: Make direct jump patching thread-safe, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 12/39] tcg: Note requirement on atomic direct jump patching, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 13/39] translate-all: remove redundant setting of tcg_ctx.code_gen_buffer_size, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 15/39] translate-all: Adjust 256mb testing for mips64, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 14/39] translate-all: add missing munmap of the code_gen guard page for MIPS, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 16/39] tcg: Clean up direct block chaining data fields, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 17/39] tcg: Use uintptr_t type for jmp_list_{next|first} fields of TB, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 18/39] tcg: Rearrange tb_link_page() to avoid forward declaration, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 19/39] tcg: Init TB's direct jumps before making it visible, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 21/39] tcg: Rename tb_jmp_remove() to tb_remove_from_jmp_list(), Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 20/39] tcg: Clarify thread safety check in tb_add_jump(),
Richard Henderson <=
- [Qemu-devel] [PULL 23/39] tcg: Clean up tb_jmp_unlink(), Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 22/39] tcg: Extract removing of jumps to TB from tb_phys_invalidate(), Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 24/39] tcg: Clean up direct block chaining safety checks, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 26/39] tcg: code_bitmap and code_write_count are not used by user-mode emulation, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 25/39] tcg: Allow goto_tb to any target PC in user mode, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 27/39] tcg: reorganize tb_find_physical loop, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 28/39] cpu-exec: elide more icount code if CONFIG_USER_ONLY, Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 29/39] tcg: Clean up from 'next_tb', Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 31/39] cpu-exec: Move TB chaining into tb_find_fast(), Richard Henderson, 2016/05/12
- [Qemu-devel] [PULL 30/39] tcg: Rework tb_invalidated_flag, Richard Henderson, 2016/05/12