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). >> >> 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 >> > > > . > -- Bin Wu