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authorJohn Stultz <johnstul@us.ibm.com>2010-07-13 17:56:18 -0700
committerThomas Gleixner <tglx@linutronix.de>2010-07-27 12:40:53 +0200
commit8c73626ab28527b7eb7f3061c027fbfe530c488c (patch)
treea3558d3fbfe59a68d4fce1b4e7b8919908a96aad /arch/frv/Kconfig
parent1a041a23da7c77b53c71fe11b4f940388bee37b1 (diff)
downloadlinux-linaro-stable-8c73626ab28527b7eb7f3061c027fbfe530c488c.tar.gz
x86: Fix vtime/file timestamp inconsistencies
Due to vtime calling vgettimeofday(), its possible that an application could call time();create("stuff",O_RDRW); only to see the file's creation timestamp to be before the value returned by time. A similar way to reproduce the issue is to compare the vsyscall time() with the syscall time(), and observe ordering issues. The modified test case from Oleg Nesterov below can illustrate this: int main(void) { time_t sec1,sec2; do { sec1 = time(&sec2); sec2 = syscall(__NR_time, NULL); } while (sec1 <= sec2); printf("vtime: %d.000000\n", sec1); printf("time: %d.000000\n", sec2); return 0; } The proper fix is to make vtime use the same time value as current_kernel_time() (which is exported via update_vsyscall) instead of vgettime(). Thanks to Jiri Olsa for bringing up the issue and catching bugs in earlier verisons of this fix. Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> LKML-Reference: <1279068988-21864-2-git-send-email-johnstul@us.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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