aboutsummaryrefslogtreecommitdiff
path: root/nptl/pthread_cancel.c
AgeCommit message (Collapse)AuthorFilesLines
2025-03-13nptl: Check if thread is already terminated in sigcancel_handler (BZ 32782)Adhemerval Zanella1-6/+8
The SIGCANCEL signal handler should not issue __syscall_do_cancel, which calls __do_cancel and __pthread_unwind, if the cancellation is already in proces (and libgcc unwind is not reentrant). Any cancellation signal received after is ignored. Checked on x86_64-linux-gnu and aarch64-linux-gnu. Tested-by: Aurelien Jarno <aurelien@aurel32.net> Reviewed-by: Florian Weimer <fweimer@redhat.com>
2025-01-01Update copyright dates with scripts/update-copyrightsPaul Eggert1-1/+1
2024-08-23nptl: Fix Race conditions in pthread cancellation [BZ#12683]Adhemerval Zanella1-49/+29
The current racy approach is to enable asynchronous cancellation before making the syscall and restore the previous cancellation type once the syscall returns, and check if cancellation has happen during the cancellation entrypoint. As described in BZ#12683, this approach shows 2 problems: 1. Cancellation can act after the syscall has returned from the kernel, but before userspace saves the return value. It might result in a resource leak if the syscall allocated a resource or a side effect (partial read/write), and there is no way to program handle it with cancellation handlers. 2. If a signal is handled while the thread is blocked at a cancellable syscall, the entire signal handler runs with asynchronous cancellation enabled. This can lead to issues if the signal handler call functions which are async-signal-safe but not async-cancel-safe. For the cancellation to work correctly, there are 5 points at which the cancellation signal could arrive: [ ... )[ ... )[ syscall ]( ... 1 2 3 4 5 1. Before initial testcancel, e.g. [*... testcancel) 2. Between testcancel and syscall start, e.g. [testcancel...syscall start) 3. While syscall is blocked and no side effects have yet taken place, e.g. [ syscall ] 4. Same as 3 but with side-effects having occurred (e.g. a partial read or write). 5. After syscall end e.g. (syscall end...*] And libc wants to act on cancellation in cases 1, 2, and 3 but not in cases 4 or 5. For the 4 and 5 cases, the cancellation will eventually happen in the next cancellable entrypoint without any further external event. The proposed solution for each case is: 1. Do a conditional branch based on whether the thread has received a cancellation request; 2. It can be caught by the signal handler determining that the saved program counter (from the ucontext_t) is in some address range beginning just before the "testcancel" and ending with the syscall instruction. 3. SIGCANCEL can be caught by the signal handler and determine that the saved program counter (from the ucontext_t) is in the address range beginning just before "testcancel" and ending with the first uninterruptable (via a signal) syscall instruction that enters the kernel. 4. In this case, except for certain syscalls that ALWAYS fail with EINTR even for non-interrupting signals, the kernel will reset the program counter to point at the syscall instruction during signal handling, so that the syscall is restarted when the signal handler returns. So, from the signal handler's standpoint, this looks the same as case 2, and thus it's taken care of. 5. For syscalls with side-effects, the kernel cannot restart the syscall; when it's interrupted by a signal, the kernel must cause the syscall to return with whatever partial result is obtained (e.g. partial read or write). 6. The saved program counter points just after the syscall instruction, so the signal handler won't act on cancellation. This is similar to 4. since the program counter is past the syscall instruction. So The proposed fixes are: 1. Remove the enable_asynccancel/disable_asynccancel function usage in cancellable syscall definition and instead make them call a common symbol that will check if cancellation is enabled (__syscall_cancel at nptl/cancellation.c), call the arch-specific cancellable entry-point (__syscall_cancel_arch), and cancel the thread when required. 2. Provide an arch-specific generic system call wrapper function that contains global markers. These markers will be used in SIGCANCEL signal handler to check if the interruption has been called in a valid syscall and if the syscalls has side-effects. A reference implementation sysdeps/unix/sysv/linux/syscall_cancel.c is provided. However, the markers may not be set on correct expected places depending on how INTERNAL_SYSCALL_NCS is implemented by the architecture. It is expected that all architectures add an arch-specific implementation. 3. Rewrite SIGCANCEL asynchronous handler to check for both canceling type and if current IP from signal handler falls between the global markers and act accordingly. 4. Adjust libc code to replace LIBC_CANCEL_ASYNC/LIBC_CANCEL_RESET to use the appropriate cancelable syscalls. 5. Adjust 'lowlevellock-futex.h' arch-specific implementations to provide cancelable futex calls. Some architectures require specific support on syscall handling: * On i386 the syscall cancel bridge needs to use the old int80 instruction because the optimized vDSO symbol the resulting PC value for an interrupted syscall points to an address outside the expected markers in __syscall_cancel_arch. It has been discussed in LKML [1] on how kernel could help userland to accomplish it, but afaik discussion has stalled. Also, sysenter should not be used directly by libc since its calling convention is set by the kernel depending of the underlying x86 chip (check kernel commit 30bfa7b3488bfb1bb75c9f50a5fcac1832970c60). * mips o32 is the only kABI that requires 7 argument syscall, and to avoid add a requirement on all architectures to support it, mips support is added with extra internal defines. Checked on aarch64-linux-gnu, arm-linux-gnueabihf, powerpc-linux-gnu, powerpc64-linux-gnu, powerpc64le-linux-gnu, i686-linux-gnu, and x86_64-linux-gnu. [1] https://lkml.org/lkml/2016/3/8/1105 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2024-01-01Update copyright dates with scripts/update-copyrightsPaul Eggert1-1/+1
2023-01-06Update copyright dates with scripts/update-copyrightsJoseph Myers1-1/+1
2022-07-05Replace __libc_multiple_threads with __libc_single_threadedAdhemerval Zanella1-1/+1
And also fixes the SINGLE_THREAD_P macro for SINGLE_THREAD_BY_GLOBAL, since header inclusion single-thread.h is in the wrong order, the define needs to come before including sysdeps/unix/sysdep.h. The macro is now moved to a per-arch single-threade.h header. The SINGLE_THREAD_P is used on some more places. Checked on aarch64-linux-gnu and x86_64-linux-gnu.
2022-04-20nptl: Fix pthread_cancel cancelhandling atomic operationsAdhemerval Zanella1-1/+2
The 404656009b reversion did not setup the atomic loop to set the cancel bits correctly. The fix is essentially what pthread_cancel did prior 26cfbb7162ad. Checked on x86_64-linux-gnu and aarch64-linux-gnu.
2022-04-14nptl: Handle spurious EINTR when thread cancellation is disabled (BZ#29029)Adhemerval Zanella1-29/+81
Some Linux interfaces never restart after being interrupted by a signal handler, regardless of the use of SA_RESTART [1]. It means that for pthread cancellation, if the target thread disables cancellation with pthread_setcancelstate and calls such interfaces (like poll or select), it should not see spurious EINTR failures due the internal SIGCANCEL. However recent changes made pthread_cancel to always sent the internal signal, regardless of the target thread cancellation status or type. To fix it, the previous semantic is restored, where the cancel signal is only sent if the target thread has cancelation enabled in asynchronous mode. The cancel state and cancel type is moved back to cancelhandling and atomic operation are used to synchronize between threads. The patch essentially revert the following commits: 8c1c0aae20 nptl: Move cancel type out of cancelhandling 2b51742531 nptl: Move cancel state out of cancelhandling 26cfbb7162 nptl: Remove CANCELING_BITMASK However I changed the atomic operation to follow the internal C11 semantic and removed the MACRO usage, it simplifies a bit the resulting code (and removes another usage of the old atomic macros). Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu, and powerpc64-linux-gnu. [1] https://man7.org/linux/man-pages/man7/signal.7.html Reviewed-by: Florian Weimer <fweimer@redhat.com> Tested-by: Aurelien Jarno <aurelien@aurel32.net>
2022-01-01Update copyright dates with scripts/update-copyrightsPaul Eggert1-1/+1
I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 7061 files FOO. I then removed trailing white space from math/tgmath.h, support/tst-support-open-dev-null-range.c, and sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following obscure pre-commit check failure diagnostics from Savannah. I don't know why I run into these diagnostics whereas others evidently do not. remote: *** 912-#endif remote: *** 913: remote: *** 914- remote: *** error: lines with trailing whitespace found ... remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
2021-09-13nptl: pthread_kill, pthread_cancel should not fail after exit (bug 19193)Florian Weimer1-4/+5
This closes one remaining race condition related to bug 12889: if the thread already exited on the kernel side, returning ESRCH is not correct because that error is reserved for the thread IDs (pthread_t values) whose lifetime has ended. In case of a kernel-side exit and a valid thread ID, no signal needs to be sent and cancellation does not have an effect, so just return 0. sysdeps/pthread/tst-kill4.c triggers undefined behavior and is removed with this commit. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-09-03Remove "Contributed by" linesSiddhesh Poyarekar1-1/+0
We stopped adding "Contributed by" or similar lines in sources in 2012 in favour of git logs and keeping the Contributors section of the glibc manual up to date. Removing these lines makes the license header a bit more consistent across files and also removes the possibility of error in attribution when license blocks or files are copied across since the contributed-by lines don't actually reflect reality in those cases. Move all "Contributed by" and similar lines (Written by, Test by, etc.) into a new file CONTRIBUTED-BY to retain record of these contributions. These contributors are also mentioned in manual/contrib.texi, so we just maintain this additional record as a courtesy to the earlier developers. The following scripts were used to filter a list of files to edit in place and to clean up the CONTRIBUTED-BY file respectively. These were not added to the glibc sources because they're not expected to be of any use in future given that this is a one time task: https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-06-23nptl: Use SA_RESTART for SIGCANCEL handlerAdhemerval Zanella1-1/+5
The usage of signals to implementation pthread cancellation is an implementation detail and should not be visible through cancellation entrypoints. However now that pthread_cancel always send the SIGCANCEL, some entrypoint might be interruptable and return EINTR to the caller (for instance on sem_wait). Using SA_RESTART hides this, since the cancellation handler should either act uppon cancellation (if asynchronous cancellation is enable) or ignore the cancellation internal signal. Checked on x86_64-linux-gnu and i686-linux-gnu.
2021-06-09nptl: Use pthread_kill on pthread_cancelAdhemerval Zanella1-5/+1
It consolidates the tgkill call and it is the first step of making pthread_cancel async-signal-safe. It also fix a possible issue where the 'struct pthread' tid is not read atomically, which might send an invalid cancellation signal (similar to what db988e50a87f613cb6b9e98a2fc66a4848bc3546 fixed for pthread_join). Checked on x86_64-linux-gnu and aarch64-linux-gnu.
2021-06-09nptl: Move cancel type out of cancelhandlingAdhemerval Zanella1-3/+3
Now that the thread cancellation type is not accessed concurrently anymore, it is possible to move it out the cancelhandling. By removing the cancel state out of the internal thread cancel handling state there is no need to check if cancelled bit was set in CAS operation. It allows simplifing the cancellation wrappers and the CANCEL_CANCELED_AND_ASYNCHRONOUS is removed. Checked on x86_64-linux-gnu and aarch64-linux-gnu.
2021-06-09nptl: Move cancel state out of cancelhandlingAdhemerval Zanella1-1/+1
Now that thread cancellation state is not accessed concurrently anymore, it is possible to move it out the 'cancelhandling'. The code is also simplified: CANCELLATION_P is replaced with a internal pthread_testcancel call and the CANCELSTATE_BIT{MASK} is removed. With this behavior pthread_setcancelstate does not require to act on cancellation if cancel type is asynchronous (is already handled either by pthread_setcanceltype or by the signal handler). Checked on x86_64-linux-gnu and aarch64-linux-gnu.
2021-06-09nptl: Remove CANCELING_BITMASKAdhemerval Zanella1-90/+35
The CANCELING_BITMASK is used as an optimization to avoid sending the signal when pthread_cancel is called in a concurrent manner. This requires then to put both the cancellation state and type on a shared state (cancelhandling), since 'pthread_cancel' checks whether cancellation is enabled and asynchrnous to either cancel itself of sending the signal. It also requires handle the CANCELING_BITMASK on __pthread_disable_asynccancel, however this incurs in the same issues described on BZ#12683: the cancellation is acted upon even *after* syscall returns with user visible side-effects. This patch removes this optimization and simplifies the pthread cancellation implementation: pthread_cancel now first checks if cancellation is already pending and if not always, sends a signal if the target is not itself. The SIGCANCEL handler is also simpified since there is not need to setup a CAS loop. It also allows to move both the cancellation state and mode out of 'cancelhadling' (it is done in subsequent patches). Checked on x86_64-linux-gnu and aarch64-linux-gnu.
2021-06-09nptl: Install cancellation handler on pthread_cancelAdhemerval Zanella1-22/+27
Now that cancellation is not used anymore to handle thread setup creation failure, the sighandle can be installed only when pthread_cancel is actually used. Checked on x86_64-linux-gnu and aarch64-linux-gnu.
2021-05-21nptl: Perform signal initialization upon pthread_createFlorian Weimer1-9/+79
Install signal handlers and unblock signals before pthread_create creates the first thread. create_thread in sysdeps/unix/sysv/linux/createthread.c can send SIGCANCEL to the current thread, so the SIGCANCEL handler is currently needed even if pthread_cancel is never called. (The way timer_create uses SIGCANCEL does not need a signal handler; both SIG_DFL and SIG_IGN dispositions should work.) Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-11nptl: Move pthread_cancel into libcFlorian Weimer1-1/+5
The symbol was moved using scripts/move-symbol-to-libc.py. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-10nptl: Eliminate __pthread_multiple_threadsFlorian Weimer1-1/+1
It is no longer needed after the SINGLE_THREADED_P consolidation. Tested-by: Carlos O'Donell <carlos@redhat.com> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-05-10nptl: Export __libc_multiple_threads from libc as an internal symbolFlorian Weimer1-1/+1
This allows the elimination of the __libc_multiple_threads_ptr variable in libpthread and its initialization procedure. Tested-by: Carlos O'Donell <carlos@redhat.com> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-04-21nptl: Move __pthread_unwind_next into libcFlorian Weimer1-1/+9
It's necessary to stub out __libc_disable_asynccancel and __libc_enable_asynccancel via rtld-stubbed-symbols because the new direct references to the unwinder result in symbol conflicts when the rtld exception handling from libc is linked in during the construction of librtld.map. unwind-forcedunwind.c is merged into unwind-resume.c. libc now needs the functions that were previously only used in libpthread. The GLIBC_PRIVATE exports of __libc_longjmp and __libc_siglongjmp are no longer needed, so switch them to hidden symbols. The symbol __pthread_unwind_next has been moved using scripts/move-symbol-to-libc.py. Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
2021-03-01nptl: Use <unwind-link.h> for accessing the libgcc_s unwinderFlorian Weimer1-1/+2
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-01-02Update copyright dates with scripts/update-copyrightsPaul Eggert1-1/+1
I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 6694 files FOO. I then removed trailing white space from benchtests/bench-pthread-locks.c and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this diagnostic from Savannah: remote: *** pre-commit check failed ... remote: *** error: lines with trailing whitespace found remote: error: hook declined to update refs/heads/master
2020-02-14linux: Remove INTERNAL_SYSCALL_DECLAdhemerval Zanella1-4/+3
With all Linux ABIs using the expected Linux kABI to indicate syscalls errors, the INTERNAL_SYSCALL_DECL is an empty declaration on all ports. This patch removes the 'err' argument on INTERNAL_SYSCALL* macro and remove the INTERNAL_SYSCALL_DECL usage. Checked with a build against all affected ABIs.
2020-01-01Update copyright dates with scripts/update-copyrights.Joseph Myers1-1/+1
2019-10-18nptl: SIGCANCEL, SIGTIMER, SIGSETXID are always definedFlorian Weimer1-7/+0
All nptl targets have these signal definitions nowadays. This changes also replaces the nptl-generic version of pthread_sigmask with the Linux version. Tested on x86_64-linux-gnu and i686-linux-gnu. Built with build-many-glibcs.py. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2019-09-07Prefer https to http for gnu.org and fsf.org URLsPaul Eggert1-1/+1
Also, change sources.redhat.com to sourceware.org. This patch was automatically generated by running the following shell script, which uses GNU sed, and which avoids modifying files imported from upstream: sed -ri ' s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g ' \ $(find $(git ls-files) -prune -type f \ ! -name '*.po' \ ! -name 'ChangeLog*' \ ! -path COPYING ! -path COPYING.LIB \ ! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \ ! -path manual/texinfo.tex ! -path scripts/config.guess \ ! -path scripts/config.sub ! -path scripts/install-sh \ ! -path scripts/mkinstalldirs ! -path scripts/move-if-change \ ! -path INSTALL ! -path locale/programs/charmap-kw.h \ ! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \ ! '(' -name configure \ -execdir test -f configure.ac -o -f configure.in ';' ')' \ ! '(' -name preconfigure \ -execdir test -f preconfigure.ac ';' ')' \ -print) and then by running 'make dist-prepare' to regenerate files built from the altered files, and then executing the following to cleanup: chmod a+x sysdeps/unix/sysv/linux/riscv/configure # Omit irrelevant whitespace and comment-only changes, # perhaps from a slightly-different Autoconf version. git checkout -f \ sysdeps/csky/configure \ sysdeps/hppa/configure \ sysdeps/riscv/configure \ sysdeps/unix/sysv/linux/csky/configure # Omit changes that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines git checkout -f \ sysdeps/powerpc/powerpc64/ppc-mcount.S \ sysdeps/unix/sysv/linux/s390/s390-64/syscall.S # Omit change that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
2019-01-01Update copyright dates with scripts/update-copyrights.Joseph Myers1-1/+1
* All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
2018-01-01Update copyright dates with scripts/update-copyrights.Joseph Myers1-1/+1
* All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
2017-06-23Clean pthread functions namespaces for C11 threadsAdhemerval Zanella1-3/+4
This patch adds internal definition (through {libc_}hidden_{proto,def}) and also change some strong to weak alias for symbols that might be used by C11 threads implementations. The patchset should not change libc/libpthread functional, although object changes are expected (since now internal symbols are used instead) and final exported symbols through GLIBC_PRIVATE is also expanded (to cover libpthread usage of __mmap{64}, __munmap, __mprotect). Checked with a build for all major ABI (aarch64-linux-gnu, alpha-linux-gnu, arm-linux-gnueabi, i386-linux-gnu, ia64-linux-gnu, m68k-linux-gnu, microblaze-linux-gnu [1], mips{64}-linux-gnu, nios2-linux-gnu, powerpc{64le}-linux-gnu, s390{x}-linux-gnu, sparc{64}-linux-gnu, tile{pro,gx}-linux-gnu, and x86_64-linux-gnu). * include/sched.h (__sched_get_priority_max): Add libc hidden proto. (__sched_get_prioriry_min): Likewise. * include/sys/mman.h (__mmap): Likewise. (__mmap64): Likewise. (__munmap): Likewise. (__mprotect): Likewise. * include/termios.h (__tcsetattr): Likewise. * include/time.h (__nanosleep): Use hidden_proto instead of libc_hidden_proto. * posix/nanosleep.c (__nanosleep): Likewise. * misc/Versions (libc): Export __mmap, __munmap, __mprotect, __sched_get_priority_min, and __sched_get_priority_max under GLIBC_PRIVATE. * nptl/allocatestack.c (__free_stacks): Use internal definition for libc symbols. (change_stack_perm): Likewise. (allocate_stack): Likewise. * sysdeps/posix/gethostname.c: Likewise. * nptl/tpp.c (__init_sched_fifo_prio): Likewise. * sysdeps/unix/sysv/linux/i386/smp.h (is_smp_system): Likewise. * sysdeps/unix/sysv/linux/powerpc/ioctl.c (__ioctl): Likewise. * nptl/pthreadP.h (__pthread_mutex_timedlock): Add definition. (__pthread_key_delete): Likewise. (__pthread_detach): Likewise. (__pthread_cancel): Likewise. (__pthread_mutex_trylock): Likewise. (__pthread_mutexattr_init): Likewise. (__pthread_mutexattr_settype): Likewise. * nptl/pthread_cancel.c (pthread_cancel): Change to internal name and create alias for exported one. * nptl/pthread_join.c (pthread_join): Likewise. * nptl/pthread_detach.c (pthread_detach): Likewise. * nptl/pthread_key_delete.c (pthread_key_delete): Likewise. * nptl/pthread_mutex_timedlock.c (pthread_mutex_timedlock): Likewise. * nptl/pthread_create.c: Change static requirements for pthread symbols. * nptl/pthread_equal.c (__pthread_equal): Change strong alias to weak for internal definition. * nptl/pthread_exit.c (__pthread_exit): Likewise. * nptl/pthread_getspecific.c (__pthread_getspecific): Likewise. * nptl/pthread_key_create.c (__pthread_key_create): Likewise. * nptl/pthread_mutex_destroy.c (__pthread_mutex_destroy): Likewise. * nptl/pthread_mutex_init.c (__pthread_mutex_init): Likewise. * nptl/pthread_mutex_lock.c (__pthread_mutex_lock): Likewise. * nptl/pthread_mutex_trylock.c (__pthread_mutex_trylock): Likewise. * nptl/pthread_mutex_unlock.c (__pthread_mutex_unlock): Likewise. * nptl/pthread_mutexattr_init.c (__pthread_mutexattr_init): Likwise. * nptl/pthread_mutexattr_settype.c (__pthread_mutexattr_settype): Likewise. * nptl/pthread_self.c (__pthread_self): Likewise. * nptl/pthread_setspecific.c (__pthread_setspecific): Likewise. * sysdeps/unix/sysv/linux/tcsetattr.c (tcsetattr): Likewise. * misc/mmap.c (__mmap): Add internal symbol definition. * misc/mmap.c (__mmap64): Likewise. * sysdeps/unix/sysv/linux/mmap.c (__mmap): Likewise. * sysdeps/unix/sysv/linux/mmap64.c (__mmap): Likewise. (__mmap64): Likewise. * sysdeps/unix/sysv/linux/i386/Versions (libc) [GLIBC_PRIVATE): Add __uname.
2017-01-01Update copyright dates with scripts/update-copyrights.Joseph Myers1-1/+1
2016-11-24Remove cached PID/TID in cloneAdhemerval Zanella1-13/+5
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: Rem