musl - musl - an implementation of the standard library for Linux-based systems

Age	Commit message (Collapse)	Author	Lines
2014-07-05	eliminate use of cached pid from thread structure	Rich Felker	-1/+1
	the main motivation for this change is to remove the assumption that the tid of the main thread is also the pid of the process. (the value returned by the set_tid_address syscall was used to fill both fields despite it semantically being the tid.) this is historically and presently true on linux and unlikely to change, but it conceivably could be false on other systems that otherwise reproduce the linux syscall api/abi. only a few parts of the code were actually still using the cached pid. in a couple places (aio and synccall) it was a minor optimization to avoid a syscall. caching could be reintroduced, but lazily as part of the public getpid function rather than at program startup, if it's deemed important for performance later. in other places (cancellation and pthread_kill) the pid was completely unnecessary; the tkill syscall can be used instead of tgkill. this is actually a rather subtle issue, since tgkill is supposedly a solution to race conditions that can affect use of tkill. however, as documented in the commit message for commit 7779dbd2663269b465951189b4f43e70839bc073, tgkill does not actually solve this race; it just limits it to happening within one process rather than between processes. we use a lock that avoids the race in pthread_kill, and the use in the cancellation signal handler is self-targeted and thus not subject to tid reuse races, so both are safe regardless of which syscall (tgkill or tkill) is used.
2012-07-12	fix several locks that weren't updated right for new futex-based __lock	Rich Felker	-2/+2
	these could have caused memory corruption due to invalid accesses to the next field. all should be fixed now; I found the errors with fgrep -r '__lock(&', which is bogus since the argument should be an array.
2012-07-12	fix pthread_kill unlocking	Rich Felker	-1/+1
	it had not been updated for the futex-based locks
2011-06-14	fix race condition in pthread_kill	Rich Felker	-1/+5
	if thread id was reused by the kernel between the time pthread_kill read it from the userspace pthread_t object and the time of the tgkill syscall, a signal could be sent to the wrong thread. the tgkill syscall was supposed to prevent this race (versus the old tkill syscall) but it can't; it can only help in the case where the tid is reused in a different process, but not when the tid is reused in the same process. the only solution i can see is an extra lock to prevent threads from exiting while another thread is trying to pthread_kill them. it should be very very cheap in the non-contended case.
2011-04-06	consistency: change all remaining syscalls to use SYS_ rather than __NR_ prefix	Rich Felker	-1/+1

2011-03-19	if returning errno value directly from a syscall, we need to negate it.	Rich Felker	-1/+1

2011-03-19	syscall overhaul part two - unify public and internal syscall interface	Rich Felker	-2/+1
	with this patch, the syscallN() functions are no longer needed; a variadic syscall() macro allows syscalls with anywhere from 0 to 6 arguments to be made with a single macro name. also, manually casting each non-integer argument with (long) is no longer necessary; the casts are hidden in the macros. some source files which depended on being able to define the old macro SYSCALL_RETURNS_ERRNO have been modified to directly use __syscall() instead of syscall(). references to SYSCALL_SIGSET_SIZE and SYSCALL_LL have also been changed. x86_64 has not been tested, and may need a follow-up commit to fix any minor bugs/oversights.
2011-02-12	initial check-in, version 0.5.0v0.5.0	Rich Felker	-0/+7