I meet two issues on an IMX6 development board without enable RTC device(so timekeeping_init will initialize the boot time and monotonic to 0).
Issue 1:exportfs -a generate: "exportfs: /opt/nfs/arm does not support NFS export" Issue 2:cat /proc/stat: "btime 4294967236" Exact reproduction of the same issues on x86 after run below code: " int main(void) { struct timeval val; int ret; val.tv_sec = 0; val.tv_usec = 0; ret = settimeofday(&val, NULL); return 0; } " Two issues are different symptoms of same problem: The reason is positive wall_to_monotonic push boot time back to the time before Epoch, getboottime will return negative value. In symptom 1: negative boot time cause get_expiry overflow time_t when input expire time is 2147483647, then cache_flush always clear entries just added in ip_map_parse. In symptom 2: show_stat use "unsigned long" to print negative value return by getboottime. This patch fix the problem. Impact: You can't set the CLOCK_REALTIME time prior to (1970 + system uptime). Signed-off-by: Wang YanQing <udkni...@gmail.com> --- Changes v1-v2: 1: fix subject, use "isn't positive" instead of "is negative". 2: rewrite changelog. 3: simplify code as suggested by John Stultz. v2-v3: 1: reword changelog, no change of source code. kernel/time/timekeeping.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index bca3667..4cdb771 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -911,6 +911,7 @@ int do_settimeofday64(const struct timespec64 *ts) struct timekeeper *tk = &tk_core.timekeeper; struct timespec64 ts_delta, xt; unsigned long flags; + int ret = 0; if (!timespec64_valid_strict(ts)) return -EINVAL; @@ -924,10 +925,15 @@ int do_settimeofday64(const struct timespec64 *ts) ts_delta.tv_sec = ts->tv_sec - xt.tv_sec; ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec; + if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) { + ret = -EINVAL; + goto out; + } + tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta)); tk_set_xtime(tk, ts); - +out: timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET); write_seqcount_end(&tk_core.seq); @@ -936,7 +942,7 @@ int do_settimeofday64(const struct timespec64 *ts) /* signal hrtimers about time change */ clock_was_set(); - return 0; + return ret; } EXPORT_SYMBOL(do_settimeofday64); @@ -965,7 +971,8 @@ int timekeeping_inject_offset(struct timespec *ts) /* Make sure the proposed value is valid */ tmp = timespec64_add(tk_xtime(tk), ts64); - if (!timespec64_valid_strict(&tmp)) { + if (timespec64_compare(&tk->wall_to_monotonic, &ts64) > 0 || + !timespec64_valid_strict(&tmp)) { ret = -EINVAL; goto error; } -- 1.8.5.6.2.g3d8a54e.dirty -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/