| Message ID | 1508445114-4717-1-git-send-email-cota@braap.org |
|---|---|
| State | New |
| Headers | show |
| Series | translate-all: exit from tb_phys_invalidate if qht_remove fails | expand |
On 10/19/2017 01:31 PM, Emilio G. Cota wrote: > Two or more threads might race while invalidating the same TB. We currently > do not check for this at all despite taking tb_lock, which means we would > wrongly invalidate the same TB more than once. This bug has actually been > hit by users: I recently saw a report on IRC, although I have yet to see > the corresponding test case. > > Fix this by using qht_remove as the synchronization point; if it fails, > that means the TB has already been invalidated, and therefore there > is nothing left to do in tb_phys_invalidate. > > Note that this solution works now that we still have tb_lock, and will > continue working once we remove tb_lock. > > Signed-off-by: Emilio G. Cota <cota@braap.org> > > --- > This patch applies on top of the "[PATCH v6 00/50] tcg tb_lock removal" series: > https://lists.gnu.org/archive/html/qemu-devel/2017-10/msg03612.html > --- > accel/tcg/translate-all.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) Applied, thanks. r~
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c index ac8dfe6..2fe8b14 100644 --- a/accel/tcg/translate-all.c +++ b/accel/tcg/translate-all.c @@ -1081,7 +1081,9 @@ void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr) phys_pc = tb->page_addr[0] + (tb->pc & ~TARGET_PAGE_MASK); h = tb_hash_func(phys_pc, tb->pc, tb->flags, tb->cflags & CF_HASH_MASK, tb->trace_vcpu_dstate); - qht_remove(&tb_ctx.htable, tb, h); + if (!qht_remove(&tb_ctx.htable, tb, h)) { + return; + } /* remove the TB from the page list */ if (tb->page_addr[0] != page_addr) {
Two or more threads might race while invalidating the same TB. We currently do not check for this at all despite taking tb_lock, which means we would wrongly invalidate the same TB more than once. This bug has actually been hit by users: I recently saw a report on IRC, although I have yet to see the corresponding test case. Fix this by using qht_remove as the synchronization point; if it fails, that means the TB has already been invalidated, and therefore there is nothing left to do in tb_phys_invalidate. Note that this solution works now that we still have tb_lock, and will continue working once we remove tb_lock. Signed-off-by: Emilio G. Cota <cota@braap.org> --- This patch applies on top of the "[PATCH v6 00/50] tcg tb_lock removal" series: https://lists.gnu.org/archive/html/qemu-devel/2017-10/msg03612.html --- accel/tcg/translate-all.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)