On Mon, Sep 15, 2014 at 03:47:41PM -0600, Justin T. Gibbs wrote: > On Aug 8, 2014, at 5:22 AM, Konstantin Belousov <kostik...@gmail.com> wrote: > > ? > > > Below is the patch which adds environment variable > > LIBPTHREAD_BIGSTACK_MAIN. Setting it to any value results in the > > main thread stack left as is, and other threads allocate stack > > below the area of RLIMIT_STACK. Try it. I do not want to set this > > behaviour as default. > > Is there a reason this should not be the default? Looking at the > getrlimit() page on the OpenGroup?s site they say: > > RLIMIT_STACK This is the maximum size of the initial thread's stack, > in bytes. The implementation does not automatically grow the stack > beyond this limit. If this limit is exceeded, SIGSEGV shall be > generated for the thread. If the thread is blocking SIGSEGV, or the > process is ignoring or catching SIGSEGV and has not made arrangements > to use an alternate stack, the disposition of SIGSEGV shall be set to > SIG_DFL before it is generated. > > Does posix say something different? > > I ran into this issue when debugging a segfault on Postgres when > running an (arguably quite bogus) query that should have fit within > both the configured stack rlimit and Postgres? configured stack limit. > The Postgres backend is really just single threaded, but happens > to pull in libpthread due to the threading support in some of the > libraries it uses. The segfault definitely violates POLA. > > ? Justin
I am conservative to not disturb the address space layout in single go. If enough people test this setting, I can consider flipping the default to the reverse. I am still curious why the things were done in this way, but nobody replied.
Description: PGP signature