[lkml]   [2012]   [Jun]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: futex system call in write
On Sun, 3 Jun 2012 01:58:55 -0400 Xin Tong wrote:
> I am a program with 2 threads, each of which calling printf in a loop.
> when i strace this programs. i see besides write() gets calls a good
> number of times. futex gets call many times as well. it seems to be
> related to the write system call ? how is the futex system call used
> here ? maybe write() is blocking and futex is used to wait the thread
> up when the write finishes ? if that is the case, what about other
> blocking system calls ?

You should probably ask this question on a glibc mailing list.

What you're seeing is the effect of using the locking version of the
standard IO calls, where before each output a mutex is acquired to
ensure thread safety. Thus futex() has nothing to do with write(), it
is merely the underlaying system call for pthread_mutex_xxxx() calls.

Mihai Donțu
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2012-06-03 12:01    [W:0.070 / U:11.728 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site