From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60303) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UsaWx-00038K-4I for qemu-devel@nongnu.org; Fri, 28 Jun 2013 11:24:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UsaWs-0000p9-4P for qemu-devel@nongnu.org; Fri, 28 Jun 2013 11:24:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35845) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UsaWr-0000ot-Su for qemu-devel@nongnu.org; Fri, 28 Jun 2013 11:24:06 -0400 Message-ID: <51CDAA8E.1070803@redhat.com> Date: Fri, 28 Jun 2013 17:23:58 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1372158807-19715-1-git-send-email-pbonzini@redhat.com> <1372158807-19715-8-git-send-email-pbonzini@redhat.com> <51CD92A6.7000309@siemens.com> In-Reply-To: <51CD92A6.7000309@siemens.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 07/11] exec: add a reference to the region returned by address_space_translate List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: peter.maydell@linaro.org, qemu-devel@nongnu.org Il 28/06/2013 15:41, Jan Kiszka ha scritto: > On 2013-06-25 13:13, Paolo Bonzini wrote: >> Once address_space_translate will only be protected by RCU, the returned >> MemoryRegion can disappear as soon as the RCU read-side critical >> section ends. Avoid this by adding a reference to the region, and >> dropping it in the caller of address_space_translate. >> >> Signed-off-by: Paolo Bonzini >> --- >> exec.c | 16 ++++++++++++++-- >> include/exec/memory.h | 3 ++- >> 2 files changed, 16 insertions(+), 3 deletions(-) >> >> diff --git a/exec.c b/exec.c >> index 5454e4d..b7f032d 100644 >> --- a/exec.c >> +++ b/exec.c >> @@ -286,6 +286,7 @@ MemoryRegion *address_space_translate(AddressSpace *as, hwaddr addr, >> >> *plen = len; >> *xlat = addr; >> + memory_region_ref(mr); >> return mr; >> } >> >> @@ -1960,6 +1961,7 @@ bool address_space_rw(AddressSpace *as, hwaddr addr, uint8_t *buf, >> memcpy(buf, ptr, l); >> } >> } >> + memory_region_unref(mr); >> len -= l; >> buf += l; >> addr += l; >> @@ -2125,8 +2127,10 @@ void *address_space_map(AddressSpace *as, >> raddr = memory_region_get_ram_addr(mr) + xlat; >> } else { >> if (memory_region_get_ram_addr(mr) + xlat != raddr + todo) { >> + memory_region_unref(mr); >> break; >> } >> + memory_region_unref(mr); >> } >> >> len -= l; > > This stage of the implementation looks inconsistent for > memory_region_get_ram_addr. Isn't the idea so far that the mr reference > is dropped again before leaving the function? memory_region_get_ram_addr is not taking a reference. address_space_map's address_space_translate is matched by the unref in address_space_unmap. You're getting the same memory region multiple times, and you have to unref it every time except the first. But there is a missing unref at the end of address_space_map (bug introduced when separating this patch from patch 11). I'll resend the series. Paolo >> @@ -2226,6 +2230,7 @@ static inline uint32_t ldl_phys_internal(hwaddr addr, >> break; >> } >> } >> + memory_region_unref(mr); >> return val; >> } >> >> @@ -2285,6 +2290,7 @@ static inline uint64_t ldq_phys_internal(hwaddr addr, >> break; >> } >> } >> + memory_region_unref(mr); >> return val; >> } >> >> @@ -2352,6 +2358,7 @@ static inline uint32_t lduw_phys_internal(hwaddr addr, >> break; >> } >> } >> + memory_region_unref(mr); >> return val; >> } >> >> @@ -2399,6 +2406,7 @@ void stl_phys_notdirty(hwaddr addr, uint32_t val) >> } >> } >> } >> + memory_region_unref(mr); >> } >> >> /* warning: addr must be aligned */ >> @@ -2440,6 +2448,7 @@ static inline void stl_phys_internal(hwaddr addr, uint32_t val, >> } >> invalidate_and_set_dirty(addr1, 4); >> } >> + memory_region_unref(mr); >> } >> >> void stl_phys(hwaddr addr, uint32_t val) >> @@ -2503,6 +2512,7 @@ static inline void stw_phys_internal(hwaddr addr, uint32_t val, >> } >> invalidate_and_set_dirty(addr1, 2); >> } >> + memory_region_unref(mr); >> } >> >> void stw_phys(hwaddr addr, uint32_t val) >> @@ -2592,11 +2602,13 @@ bool cpu_physical_memory_is_io(hwaddr phys_addr) >> { >> MemoryRegion*mr; >> hwaddr l = 1; >> + bool res; >> >> mr = address_space_translate(&address_space_memory, >> phys_addr, &phys_addr, &l, false); >> >> - return !(memory_region_is_ram(mr) || >> - memory_region_is_romd(mr)); >> + res = !(memory_region_is_ram(mr) || memory_region_is_romd(mr)); >> + memory_region_unref(mr); >> + return res; >> } >> #endif > > Unless I'm missing something ATM, address_space_access_valid, > cpu_physical_memory_write_rom and tb_invalidate_phys_addr also require > unref calls. > >> diff --git a/include/exec/memory.h b/include/exec/memory.h >> index c842d48..2a37b2c 100644 >> --- a/include/exec/memory.h >> +++ b/include/exec/memory.h >> @@ -1003,7 +1003,8 @@ bool address_space_write(AddressSpace *as, hwaddr addr, >> bool address_space_read(AddressSpace *as, hwaddr addr, uint8_t *buf, int len); >> >> /* address_space_translate: translate an address range into an address space >> - * into a MemoryRegion and an address range into that section >> + * into a MemoryRegion and an address range into that section. Add a reference >> + * to that region. >> * >> * @as: #AddressSpace to be accessed >> * @addr: address within that address space >> > > Jan >