This patch remove the PID cache and usage in current GLIBC code. Current
usage is mainly used a performance optimization to avoid the syscall,
however it adds some issues:
- The exposed clone syscall will try to set pid/tid to make the new
thread somewhat compatible with current GLIBC assumptions. This cause
a set of issue with new workloads and usecases (such as BZ#17214 and
[1]) as well for new internal usage of clone to optimize other algorithms
(such as clone plus CLONE_VM for posix_spawn, BZ#19957).
- The caching complexity also added some bugs in the past [2] [3] and
requires more effort of each port to handle such requirements (for
both clone and vfork implementation).
- Caching performance gain in mainly on getpid and some specific
code paths. The getpid performance leverage is questionable [4],
either by the idea of getpid being a hotspot as for the getpid
implementation itself (if it is indeed a justifiable hotspot a
vDSO symbol could let to a much more simpler solution).
Other usage is mainly for non usual code paths, such as pthread
cancellation signal and handling.
For thread creation (on stack allocation) the code simplification in fact
adds some performance gain due the no need of transverse the stack cache
and invalidate each element pid.
Other thread usages will require a direct getpid syscall, such as
cancellation/setxid signal, thread cancellation, thread fail path (at
create_thread), and thread signal (pthread_kill and pthread_sigqueue).
However these are hardly usual hotspots and I think adding a syscall is
justifiable.
It also simplifies both the clone and vfork arch-specific implementation.
And by review each fork implementation there are some discrepancies that
this patch also solves:
- microblaze clone/vfork does not set/reset the pid/tid field
- hppa uses the default vfork implementation that fallback to fork.
Since vfork is deprecated I do not think we should bother with it.
The patch also removes the TID caching in clone. My understanding for
such semantic is try provide some pthread usage after a user program
issue clone directly (as done by thread creation with CLONE_PARENT_SETTID
and pthread tid member). However, as stated before in multiple discussions
threads, GLIBC provides clone syscalls without further supporting all this
semantics.
I ran a full make check on x86_64, x32, i686, armhf, aarch64, and powerpc64le.
For sparc32, sparc64, and mips I ran the basic fork and vfork tests from
posix/ folder (on a qemu system). So it would require further testing
on alpha, hppa, ia64, m68k, nios2, s390, sh, and tile (I excluded microblaze
because it is already implementing the patch semantic regarding clone/vfork).
[1] https://codereview.chromium.org/800183004/
[2] https://sourceware.org/ml/libc-alpha/2006-07/msg00123.html
[3] https://sourceware.org/bugzilla/show_bug.cgi?id=15368
[4] http://yarchive.net/comp/linux/getpid_caching.html
* sysdeps/nptl/fork.c (__libc_fork): Remove pid cache setting.
* nptl/allocatestack.c (allocate_stack): Likewise.
(__reclaim_stacks): Likewise.
(setxid_signal_thread): Obtain pid through syscall.
* nptl/nptl-init.c (sigcancel_handler): Likewise.
(sighandle_setxid): Likewise.
* nptl/pthread_cancel.c (pthread_cancel): Likewise.
* sysdeps/unix/sysv/linux/pthread_kill.c (__pthread_kill): Likewise.
* sysdeps/unix/sysv/linux/pthread_sigqueue.c (pthread_sigqueue):
Likewise.
* sysdeps/unix/sysv/linux/createthread.c (create_thread): Likewise.
* sysdeps/unix/sysv/linux/getpid.c: Remove file.
* nptl/descr.h (struct pthread): Change comment about pid value.
* nptl/pthread_getattr_np.c (pthread_getattr_np): Remove thread
pid assert.
* sysdeps/unix/sysv/linux/pthread-pids.h (__pthread_initialize_pids):
Do not set pid value.
* nptl_db/td_ta_thr_iter.c (iterate_thread_list): Remove thread
pid cache check.
* nptl_db/td_thr_validate.c (td_thr_validate): Likewise.
* sysdeps/aarch64/nptl/tcb-offsets.sym: Remove pid offset.
* sysdeps/alpha/nptl/tcb-offsets.sym: Likewise.
* sysdeps/arm/nptl/tcb-offsets.sym: Likewise.
* sysdeps/hppa/nptl/tcb-offsets.sym: Likewise.
* sysdeps/i386/nptl/tcb-offsets.sym: Likewise.
* sysdeps/ia64/nptl/tcb-offsets.sym: Likewise.
* sysdeps/m68k/nptl/tcb-offsets.sym: Likewise.
* sysdeps/microblaze/nptl/tcb-offsets.sym: Likewise.
* sysdeps/mips/nptl/tcb-offsets.sym: Likewise.
* sysdeps/nios2/nptl/tcb-offsets.sym: Likewise.
* sysdeps/powerpc/nptl/tcb-offsets.sym: Likewise.
* sysdeps/s390/nptl/tcb-offsets.sym: Likewise.
* sysdeps/sh/nptl/tcb-offsets.sym: Likewise.
* sysdeps/sparc/nptl/tcb-offsets.sym: Likewise.
* sysdeps/tile/nptl/tcb-offsets.sym: Likewise.
* sysdeps/x86_64/nptl/tcb-offsets.sym: Likewise.
* sysdeps/unix/sysv/linux/aarch64/clone.S: Remove pid and tid caching.
* sysdeps/unix/sysv/linux/alpha/clone.S: Likewise.
* sysdeps/unix/sysv/linux/arm/clone.S: Likewise.
* sysdeps/unix/sysv/linux/hppa/clone.S: Likewise.
* sysdeps/unix/sysv/linux/i386/clone.S: Likewise.
* sysdeps/unix/sysv/linux/ia64/clone2.S: Likewise.
* sysdeps/unix/sysv/linux/mips/clone.S: Likewise.
* sysdeps/unix/sysv/linux/nios2/clone.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sh/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/tile/clone.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/aarch64/vfork.S: Remove pid set and reset.
* sysdeps/unix/sysv/linux/alpha/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/arm/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/i386/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/ia64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/m68k/clone.S: Likewise.
* sysdeps/unix/sysv/linux/m68k/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/mips/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/nios2/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/sh/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/tile/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/vfork.S: Likewise.
* sysdeps/unix/sysv/linux/tst-clone2.c (f): Remove direct pthread
struct access.
(clone_test): Remove function.
(do_test): Rewrite to take in consideration pid is not cached anymore.
I've moved the ARM port from ports to the main sysdeps hierarchy.
Beyond the README update, the move of the files was simply
git mv ports/sysdeps/arm sysdeps/arm
git mv ports/sysdeps/unix/arm sysdeps/unix/arm
git mv ports/sysdeps/unix/sysv/linux/arm sysdeps/unix/sysv/linux/arm
and in addition to the ChangeLog entries here, I put a note at the top
of ports/ChangeLog.arm similar to that at the top of
ChangeLog.powerpc. There is deliberately no NEWS change, as I think
it makes the most sense to put in a general note above all ports
having moved if we can achieve that for 2.20.
Tested that disassembly of installed shared libraries for arm is the
same before and after this patch, except for data (not instructions)
in ld.so (there are assertions in sysdeps/arm/dl-machine.h, and the
path by which that file is found, and so by which it appears in the
assertion message, changes as a result of the move).
* sysdeps/arm: Move directory from ports/sysdeps/arm.
* sysdeps/unix/arm: Move directory from ports/sysdeps/unix/arm.
* sysdeps/unix/sysv/linux/arm: Move directory from
ports/sysdeps/unix/sysv/linux/arm.
* README: Update listing for arm-*-linux-gnueabi.
ports/ChangeLog.arm:
* sysdeps/arm: Move directory to ../sysdeps/arm.
* sysdeps/unix/arm: Move directory to ../sysdeps.arm.
* sysdeps/unix/sysv/linux/arm: Move directory to
../sysdeps/unix/sysv/linux/arm.
Use it instead of __THUMB_INTERWORK__. Make RETINSTR take
only a condition and a register.
* sysdeps/arm/dl-machine.h: Use __USE_BX__ instead of
__THUMB_INTERWORK__.
(_dl_start_user): Use BX.
* sysdeps/arm/strlen.S: Use DO_RET.
* sysdeps/unix/arm/brk.S, sysdeps/unix/arm/fork.S,
sysdeps/unix/arm/sysdep.S, sysdeps/unix/arm/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/arm/clone.S,
sysdeps/unix/sysv/linux/arm/mmap.S,
sysdeps/unix/sysv/linux/arm/mmap64.S,
sysdeps/unix/sysv/linux/arm/socket.S,
sysdeps/unix/sysv/linux/arm/sysdep.h,
sysdeps/unix/sysv/linux/arm/vfork.S: Update uses of RETINSTR.
2003-09-17 Philip Blundell <philb@gnu.org>
* sysdeps/unix/sysv/linux/arm/vfork.S: Branch to fork if
libpthread is loaded. Elide backwards compatibility code when not
required.
* sysdeps/unix/sysv/linux/kernel-features.h
(__ASSUME_VFORK_SYSCALL): Define for kernel 2.4 on arm.
* sysdeps/unix/sysv/linux/arm/vfork.S: Elide compatibility code
when __ASSUME_VFORK_SYSCALL is defined.
* sysdeps/unix/sysv/linux/arm/mmap64.S: Likewise for
__ASSUME_MMAP2_SYSCALL.
* sysdeps/unix/sysv/linux/arm/sigaction.c: Likewise for
__ASSUME_REALTIME_SIGNALS.
2001-07-06 Paul Eggert <eggert@twinsun.com>
* manual/argp.texi: Remove ignored LGPL copyright notice; it's
not appropriate for documentation anyway.
* manual/libc-texinfo.sh: "Library General Public License" ->
"Lesser General Public License".
2001-07-06 Andreas Jaeger <aj@suse.de>
* All files under GPL/LGPL version 2: Place under LGPL version
2.1.
1999-04-12 Philip Blundell <philb@gnu.org>
* elf/elf.h: Update ARM definitions to match current gas2.
* sysdeps/arm/bits/endian.h: Support big endian operation.
* sysdeps/unix/sysv/linux/arm/ioperm.c (_outw, _outb, _outl):
Don't bother range checking the port number.
* sysdeps/unix/sysv/linux/arm/vfork.S: New file.
* sysdeps/unix/sysv/linux/arm/sysdep.h (INLINE_SYSCALL): Include
the syscall name in assembler output for ease of debugging.
* sysdeps/unix/sysv/linux/arm/sigaction.c: Don't rely on undefined
compiler behaviour.
* sysdeps/unix/sysv/linux/arm/sigrestorer.S: New file.
* sysdeps/unix/sysv/linux/arm/Makefile [$(subdir) = signal]
(sysdep_routines): Add sigrestorer.
* string/tester.c (test_strcpy): Add new tests for unaligned
arguments.
* sysdeps/arm/bits/string.h: Delete inline implementations of
strcpy and stpcpy.
1999-01-28 Andreas Schwab <schwab@issan.cs.uni-dortmund.de>
* sysdeps/wordsize-32/stdint.h (INT8_C, INT16_C, INT32_C, INT64_C,
UINT8_C, UINT16_C, UINT32_C, UINT64_C): Remove casts, they must be
integer constants. Use ## directly instead of __CONCAT so that
the suffix string is not expanded as a macro.
* sysdeps/wordsize-64/stdint.h (INT8_C, INT16_C, INT32_C, INT64_C,
UINT8_C, UINT16_C, UINT32_C, UINT64_C): Likewise.
(INT64_MIN, INT64_MAX, UINT64_MAX, INT_LEAST64_MIN,
INT_LEAST64_MAX, UINT_LEAST64_MAX, INT_FAST16_MIN, INT_FAST32_MIN,
INT_FAST64_MIN, INT_FAST16_MAX, INT_FAST32_MAX, INT_FAST64_MAX,
UINT_FAST16_MAX, UINT_FAST32_MAX, UINT_FAST64_MAX, INTMAX_MIN,
INTMAX_MAX, UINTMAX_MAX): Define as long constants, not long long.
1999-01-28 Andreas Schwab <schwab@issan.cs.uni-dortmund.de>
* locale/mb_cur_max.c (__ctype_get_mb_cur_max): Correct return
type to size_t.
* locale/broken_cur_max.c (__ctype_get_mb_cur_max): Likewise.
* stdlib/stdlib.h (__ctype_get_mb_cur_max): Likewise.
1999-01-27 Philip Blundell <pb@nexus.co.uk>
* sysdeps/unix/sysv/linux/arm/vfork.S: Deleted.
1999-01-20 Philip Blundell <pb@nexus.co.uk>
* sysdeps/unix/sysv/linux/arm/sigaction.c: New file.
* sysdeps/unix/sysv/linux/arm/vfork.S: New file.
* sysdeps/unix/sysv/linux/arm/Dist: Add vfork.S.
* sysdeps/unix/sysv/linux/arm/clone.S: Optimise a little, support
26-bit machines correctly and fix check for returned errors.
