On 5/15/2015 3:40 AM, Konstantin Belousov wrote: > Author: kib > Date: Fri May 15 08:40:17 2015 > New Revision: 282948 > URL: https://svnweb.freebsd.org/changeset/base/282948 > > Log: > Some third-party malloc(3) implementations use pthread_setspecific(3) > to handle per-thread information. Since our pthread_setspecific() > implementation calls calloc(3) to allocate per-thread specific data > storage, things get complicated. > > Switch the allocator to use bare mmap(2). There is some loss of the > allocated page, since e.g. on amd64, PTHREAD_KEYS_MAX * sizeof(struct > pthread_specific_elem) is 3K (it actually spans whole page due to > padding), but I believe it is more acceptable than additional code for > specialized allocator(). > > The alternatives would either to make the specific data array be part of > the struct thread, or use internal bindings to call the libc malloc, > avoiding interposing. > > Also do the style pass over the thr_spec.c, esp. simplify the > conditionals nesting by returning early when an error detected. > Remove trivial comments. > > Found by: y...@rawbw.com > PR: 200138 > Sponsored by: The FreeBSD Foundation > MFC after: 2 weeks > > Modified: > head/lib/libthr/thread/thr_spec.c >
Thank you for this! I have a lot of patches at Isilon for adding a libc cleanup function to free all caching, for use in memory leak detectors such as valgrind. I even fixed valgrind to utilize it. This particular code was problematic. I wrote up an arch mail about my patch a few months ago and it ended up being several pages about libthr. I never sent it because it became too long. I need to revisit that work and get an arch@ discussion going on my proposal and the various issues I ran into with libthr. While developing this cleanup feature, and working on a malloc wrapper (dmalloc), I had a lot of problems with pthread_mutext_t (and similar primitives) using calloc(3). I found that David Xu actually did do most of the work to change this but abandoned it (it's all in SVN still). Using pthreads from a malloc wrapper is really painful to get right. -- Regards, Bryan Drewery
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