On 02/10/2015 11:48 AM, Bin Wu wrote: > On 2015/2/10 11:16, Wen Congyang wrote: >> On 02/09/2015 10:48 PM, Stefan Hajnoczi wrote: >>> On Mon, Feb 09, 2015 at 02:50:39PM +0800, Bin Wu wrote: >>>> From: Bin Wu <wu.wu...@huawei.com> >>>> >>>> We tested VMs migration with their disk images by drive_mirror. With >>>> migration, two VMs copyed large files between each other. During the >>>> test, a segfault occured. The stack was as follow: >>>> >>>> (gdb) bt >>>> qemu-coroutine-lock.c:66 >>>> to=0x7fa5a1798648) at qemu-coroutine.c:97 >>>> request=0x7fa28c2ffa10, reply=0x7fa28c2ffa30, qiov=0x0, offset=0) at >>>> block/nbd-client.c:165 >>>> sector_num=8552704, nb_sectors=2040, qiov=0x7fa5a1757468, offset=0) at >>>> block/nbd-client.c:262 >>>> sector_num=8552704, nb_sectors=2048, qiov=0x7fa5a1757468) at >>>> block/nbd-client.c:296 >>>> nb_sectors=2048, qiov=0x7fa5a1757468) at block/nbd.c:291 >>>> req=0x7fa28c2ffbb0, offset=4378984448, bytes=1048576, qiov=0x7fa5a1757468, >>>> flags=0) at block.c:3321 >>>> offset=4378984448, bytes=1048576, qiov=0x7fa5a1757468, flags=(unknown: 0)) >>>> at >>>> block.c:3447 >>>> sector_num=8552704, nb_sectors=2048, qiov=0x7fa5a1757468, flags=(unknown: >>>> 0)) at >>>> block.c:3471 >>>> nb_sectors=2048, qiov=0x7fa5a1757468) at block.c:3480 >>>> nb_sectors=2048, qiov=0x7fa5a1757468) at block/raw_bsd.c:62 >>>> req=0x7fa28c2ffe30, offset=4378984448, bytes=1048576, qiov=0x7fa5a1757468, >>>> flags=0) at block.c:3321 >>>> offset=4378984448, bytes=1048576, qiov=0x7fa5a1757468, flags=(unknown: 0)) >>>> at >>>> block.c:3447 >>>> sector_num=8552704, nb_sectors=2048, qiov=0x7fa5a1757468, flags=(unknown: >>>> 0)) at >>>> block.c:3471 >>>> coroutine-ucontext.c:121 >>> >>> This backtrace is incomplete. Where are the function names? The >>> parameter lists appear incomplete too. >>> >>>> After analyzing the stack and reviewing the code, we find the >>>> qemu_co_queue_run_restart should not be put in the coroutine_swap function >>>> which >>>> can be invoked by qemu_coroutine_enter or qemu_coroutine_yield. Only >>>> qemu_coroutine_enter needs to restart the co_queue. >>>> >>>> The error scenario is as follow: coroutine C1 enters C2, C2 yields >>>> back to C1, then C1 ternimates and the related coroutine memory >>>> becomes invalid. After a while, the C2 coroutine is entered again. >>>> At this point, C1 is used as a parameter passed to >>>> qemu_co_queue_run_restart. Therefore, qemu_co_queue_run_restart >>>> accesses an invalid memory and a segfault error ocurrs. >>>> >>>> The qemu_co_queue_run_restart function re-enters coroutines waiting >>>> in the co_queue. However, this function should be only used int the >>>> qemu_coroutine_enter context. Only in this context, when the current >>>> coroutine gets execution control again(after the execution of >>>> qemu_coroutine_switch), we can restart the target coutine because the >>>> target coutine has yielded back to the current coroutine or it has >>>> terminated. >>>> >>>> First we want to put qemu_co_queue_run_restart in qemu_coroutine_enter, >>>> but we find we can not access the target coroutine if it terminates. >>> >>> This example captures the scenario you describe: >>> >>> diff --git a/qemu-coroutine.c b/qemu-coroutine.c >>> index 525247b..883cbf5 100644 >>> --- a/qemu-coroutine.c >>> +++ b/qemu-coroutine.c >>> @@ -103,7 +103,10 @@ static void coroutine_swap(Coroutine *from, Coroutine >>> *to) >>> { >>> CoroutineAction ret; >>> >>> + fprintf(stderr, "> %s from %p to %p\n", __func__, from, to); >>> ret = qemu_coroutine_switch(from, to, COROUTINE_YIELD); >>> + fprintf(stderr, "< %s from %p to %p switch %s\n", __func__, from, to, >>> + ret == COROUTINE_YIELD ? "yield" : "terminate"); >>> >>> qemu_co_queue_run_restart(to); >>> >>> @@ -111,6 +114,7 @@ static void coroutine_swap(Coroutine *from, Coroutine >>> *to) >>> case COROUTINE_YIELD: >>> return; >>> case COROUTINE_TERMINATE: >>> + fprintf(stderr, "coroutine_delete %p\n", to); >>> trace_qemu_coroutine_terminate(to); >>> coroutine_delete(to); >>> return; >>> diff --git a/tests/test-coroutine.c b/tests/test-coroutine.c >>> index 27d1b6f..d44c428 100644 >>> --- a/tests/test-coroutine.c >>> +++ b/tests/test-coroutine.c >>> @@ -13,6 +13,7 @@ >>> >>> #include <glib.h> >>> #include "block/coroutine.h" >>> +#include "block/coroutine_int.h" >>> >>> /* >>> * Check that qemu_in_coroutine() works >>> @@ -122,6 +123,35 @@ static void test_yield(void) >>> g_assert_cmpint(i, ==, 5); /* coroutine must yield 5 times */ >>> } >>> >>> +static void coroutine_fn c2_fn(void *opaque) >>> +{ >>> + fprintf(stderr, "c2 Part 1\n"); >>> + qemu_coroutine_yield(); >>> + fprintf(stderr, "c2 Part 2\n"); >>> +} >>> + >>> +static void coroutine_fn c1_fn(void *opaque) >>> +{ >>> + Coroutine *c2 = opaque; >>> + >>> + fprintf(stderr, "c1 Part 1\n"); >>> + qemu_coroutine_enter(c2, NULL); >>> + fprintf(stderr, "c1 Part 2\n"); >>> +} >>> + >>> +static void test_co_queue(void) >>> +{ >>> + Coroutine *c1; >>> + Coroutine *c2; >>> + >>> + c1 = qemu_coroutine_create(c1_fn); >>> + c2 = qemu_coroutine_create(c2_fn); >>> + >>> + qemu_coroutine_enter(c1, c2); >>> + memset(c1, 0xff, sizeof(Coroutine)); >>> + qemu_coroutine_enter(c2, NULL); >>> +} >>> + >>> /* >>> * Check that creation, enter, and return work >>> */ >>> @@ -343,6 +373,7 @@ static void perf_cost(void) >>> int main(int argc, char **argv) >>> { >>> g_test_init(&argc, &argv, NULL); >>> + g_test_add_func("/basic/co_queue", test_co_queue); >>> g_test_add_func("/basic/lifecycle", test_lifecycle); >>> g_test_add_func("/basic/yield", test_yield); >>> g_test_add_func("/basic/nesting", test_nesting); >>> >>> Here is the output (with printfs in coroutine_swap): >>> >>> -> coroutine_swap from MAIN to C1 >>> c1 Part 1 >>> -> coroutine_swap from C1 to C2 >>> c2 Part 1 >>> -> coroutine_swap from C2 to C1 >>> <- coroutine_swap from C1 to C2 switch yield >>> c1 Part 2 >>> <- coroutine_swap from MAIN to C1 switch terminate >>> coroutine_delete C1 >>> -> coroutine_swap from MAIN to C2 >>> <- coroutine_swap from C2 to C1 switch yield !!! >>> c2 Part 2 >>> <- coroutine_swap from MAIN to C2 switch terminate >>> coroutine_delete C2 >>> >>> I have marked the problematic line with "!!!". The to=C1 variable is >>> used after C1 has been deleted. >> >> How to build the test program? make test? I meet the following errors: >> make test >> make -C tests/tcg test >> make[1]: Entering directory '/work/src/qemu/tests/tcg' >> CC test_path.o >> In file included from /work/src/qemu/include/qemu-common.h:43:0, >> from /work/src/qemu/util/cutils.c:24, >> from test_path.c:3: >> /work/src/qemu/include/glib-compat.h:19:18: fatal error: glib.h: No such >> file or directory >> #include <glib.h> >> ^ >> compilation terminated. >> /work/src/qemu/rules.mak:57: recipe for target 'test_path.o' failed >> make[1]: *** [test_path.o] Error 1 >> make[1]: Leaving directory '/work/src/qemu/tests/tcg' >> Makefile:428: recipe for target 'test' failed >> make: *** [test] Error 2 >> >> Do I miss something? >> >> Thanks >> Wen Congyang >> > > First, you need to install glib2-devel package which includes the glib.h. Then > you can use "make check" in the source tree to compile and run all tests (or > use > "make check-help" to get some helps).
I have installed glib2-devel, and "make check" can work, but "make test" cannot work... Thanks Wen Congyang > >>> >>> The test crashes since it writes 0xff to C1 after it has terminated. >>> >>>> Signed-off-by: Bin Wu <wu.wu...@huawei.com> >>>> --- >>>> qemu-coroutine.c | 16 ++++++++++------ >>>> 1 file changed, 10 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/qemu-coroutine.c b/qemu-coroutine.c >>>> index 525247b..cc0bdfa 100644 >>>> --- a/qemu-coroutine.c >>>> +++ b/qemu-coroutine.c >>>> @@ -99,29 +99,31 @@ static void coroutine_delete(Coroutine *co) >>>> qemu_coroutine_delete(co); >>>> } >>>> >>>> -static void coroutine_swap(Coroutine *from, Coroutine *to) >>>> +static CoroutineAction coroutine_swap(Coroutine *from, Coroutine *to) >>>> { >>>> CoroutineAction ret; >>>> >>>> ret = qemu_coroutine_switch(from, to, COROUTINE_YIELD); >>>> >>>> - qemu_co_queue_run_restart(to); >>>> - >>>> switch (ret) { >>>> case COROUTINE_YIELD: >>>> - return; >>>> + break; >>>> case COROUTINE_TERMINATE: >>>> trace_qemu_coroutine_terminate(to); >>>> + qemu_co_queue_run_restart(to); >>>> coroutine_delete(to); >>>> - return; >>>> + break; >>>> default: >>>> abort(); >>>> } >>>> + >>>> + return ret; >>>> } >>>> >>>> void qemu_coroutine_enter(Coroutine *co, void *opaque) >>>> { >>>> Coroutine *self = qemu_coroutine_self(); >>>> + CoroutineAction ret; >>>> >>>> trace_qemu_coroutine_enter(self, co, opaque); >>>> >>>> @@ -132,7 +134,9 @@ void qemu_coroutine_enter(Coroutine *co, void *opaque) >>>> >>>> co->caller = self; >>>> co->entry_arg = opaque; >>>> - coroutine_swap(self, co); >>>> + ret = coroutine_swap(self, co); >>>> + if (ret == COROUTINE_YIELD) >>>> + qemu_co_queue_run_restart(co); >>>> } >>> >>> Your fix looks correct although QEMU coding style requires {}. >>> >>> I tried to think of a simpler solution that keeps a single >>> qemu_co_queue_run_restart() call but was unable to find one. >>> >>> Please send another revision with a test-coroutine.c test case so we can >>> protect against regressions. >>> >>> Thanks, >>> Stefan >>> >> >> >> . >> >