mysql_client uses some inline assembly code to switch thread stacks.
This works, however tools that perform backtrace get confused to fix
this we write a specific constant to signify bottom of stack. This
constant is needed when compiling with CLang as well.
The check inserts a DWARF directive to tell stack unwinding that the
bottom of the (co-routine) stack has been reached. Without this, stack
traces may attempt to continue past the bottom of the stack.
The GCC version check was incorrect, and failed to trigger for GCC
version 5.[0123].
Non-blocking client currently can be build on Windows, GCC on i386 and x64, or any OS wth ucontext.h header. Prior to this patch, build failed if neither of these conditions is true.
Fix to avoid compiler errors in these case - non-blocking API would not be useful on , but otherwise everything will work as before.
- Ensure asm parameters are in registers, so we do not de-reference from
bogus stack pointer.
- Make return address undefined in DWARF unwind info in my_context_spawn,
so DWARF-based unwinders will know this is the end of the call stack
(same as the amd64 fix for the similar issue).
Fix memory leak in one error case in mysqldump.
Fix that HAVE_VALGRIND_VALGRIND_H is now HAVE_VALGRIND in 5.5.
Fix that @have_ssl should not be set in embedded (introduced when
removing #undef HAVE_OPENSSL from my_global.h).
Main change is that non-blocking operation is now an option that must be
explicitly enabled with mysql_option(mysql, MYSQL_OPT_NONBLOCK, ...)
before any non-blocing operation can be used.
Also the CLIENT_REMEMBER_OPTIONS flag is now always enabled and thus
effectively ignored (it was not really useful anyway, and this simplifies
things when non-blocking mysql_real_connect() fails).
All client functions that can block on I/O have alternate _start() and
_cont() versions that do not block but return control back to the
application, which can then issue I/O wait in its own fashion and later
call back into the library to continue the operation.
Works behind the scenes by spawning a co-routine/fiber to run the
blocking operation and suspend it while waiting for I/O. This
co-routine/fiber use is invisible to applications.
For i368/x86_64 on GCC, uses very fast assembler co-routine support. On
Windows uses native Win32 Fibers. Falls back to POSIX ucontext on other
platforms. Assembler routines for more platforms are relatively easy to
add by extending mysys/my_context.c, eg. similar to the Lua lcoco
library.
For testing, mysqltest and mysql_client_test are extended with the
option --non-blocking-api. This causes the programs to use the
non-blocking API for database access. mysql-test-run.pl has a similar
option --non-blocking-api that uses this, as well as additional
testcases.
An example program tests/async_queries.c is included that uses the new
non-blocking API with libevent to show how, in a single-threaded
program, to issue many queries in parallel against a database.
client/async_example.c:
Fix const warning
******
Fix bug with wrong timeout value for poll().
include/Makefile.am:
Fix missing include for `make dist`
include/mysql.h:
Add prototypes for all non-blocking API calls.
include/mysql.h.pp:
Add prototypes for all non-blocking API calls.
mysys/my_context.c:
Fix type warning for makecontext() function pointer argument.
sql-common/mysql_async.c:
Fix crashes in the non-blocking API for functions that can take MYSQL argument
that is NULL.
tests/Makefile.am:
Add header file to `make dist`
tests/mysql_client_test.c:
Replace blocking calls with wrappers around the non-blocking calls, used in
mysql_client_test to test the new non-blocking API.
tests/nonblock-wrappers.h:
Replace blocking calls with wrappers around the non-blocking calls, used in
mysql_client_test to test the new non-blocking API.
