<p>Stefan Sperling has uploaded this change for <strong>review</strong>.</p><p><a href="https://gerrit.osmocom.org/10488">View Change</a></p><pre style="font-family: monospace,monospace; white-space: pre-wrap;">fix timespec subtraction in compute_elapsed_us()<br><br>The previous implementation unconditionally subtracted nanosecond<br>values from different time measurements, causing overflow if the<br>current measurement was taken in less of a fraction of a second<br>than the past measurement. Use timespecsub() instead, which<br>accounts for nanoseconds correctly.<br>This is a similar bug as fixed in osmo-pcu for issue OS#3225<br><br>While here, switch variables which are calculated based on<br>struct timespec to 64 bit types. While probably not strictly necessary<br>in practice, this makes the types used in calculations more compatible.<br><br>Change-Id: Idfd9c807e35cd7fb5c80625b9746121f81c24599<br>Related: OS#3467<br>Related: OS#3225<br>---<br>M src/osmo-bts-trx/scheduler_trx.c<br>1 file changed, 11 insertions(+), 12 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;">git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/88/10488/1</pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/src/osmo-bts-trx/scheduler_trx.c b/src/osmo-bts-trx/scheduler_trx.c</span><br><span>index 4ab937a..4bac235 100644</span><br><span>--- a/src/osmo-bts-trx/scheduler_trx.c</span><br><span>+++ b/src/osmo-bts-trx/scheduler_trx.c</span><br><span>@@ -30,6 +30,7 @@</span><br><span> </span><br><span> #include <osmocom/core/msgb.h></span><br><span> #include <osmocom/core/talloc.h></span><br><span style="color: hsl(120, 100%, 40%);">+#include <osmocom/core/timer_compat.h></span><br><span> #include <osmocom/codec/codec.h></span><br><span> #include <osmocom/codec/ecu.h></span><br><span> #include <osmocom/core/bits.h></span><br><span>@@ -1409,13 +1410,12 @@</span><br><span> #define TRX_LOSS_FRAMES 400</span><br><span> </span><br><span> /*! compute the number of micro-seconds difference elapsed between \a last and \a now */</span><br><span style="color: hsl(0, 100%, 40%);">-static inline int compute_elapsed_us(const struct timespec *last, const struct timespec *now)</span><br><span style="color: hsl(120, 100%, 40%);">+static inline int64_t compute_elapsed_us(const struct timespec *last, const struct timespec *now)</span><br><span> {</span><br><span style="color: hsl(0, 100%, 40%);">- int elapsed;</span><br><span style="color: hsl(120, 100%, 40%);">+ struct timespec elapsed;</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- elapsed = (now->tv_sec - last->tv_sec) * 1000000</span><br><span style="color: hsl(0, 100%, 40%);">- + (now->tv_nsec - last->tv_nsec) / 1000;</span><br><span style="color: hsl(0, 100%, 40%);">- return elapsed;</span><br><span style="color: hsl(120, 100%, 40%);">+ timespecsub(now, last, &elapsed);</span><br><span style="color: hsl(120, 100%, 40%);">+ return (int64_t)(elapsed.tv_sec * 1000000) + (elapsed.tv_nsec / 1000);</span><br><span> }</span><br><span> </span><br><span> /*! compute the number of frame number intervals elapsed between \a last and \a now */</span><br><span>@@ -1508,8 +1508,7 @@</span><br><span> struct osmo_trx_clock_state *tcs = &g_clk_s;</span><br><span> struct timespec tv_now;</span><br><span> uint64_t expire_count;</span><br><span style="color: hsl(0, 100%, 40%);">- int elapsed_us;</span><br><span style="color: hsl(0, 100%, 40%);">- int error_us;</span><br><span style="color: hsl(120, 100%, 40%);">+ int64_t elapsed_us, error_us;</span><br><span> int rc, i;</span><br><span> </span><br><span> if (!(what & BSC_FD_READ))</span><br><span>@@ -1537,14 +1536,14 @@</span><br><span> elapsed_us = compute_elapsed_us(&tcs->last_fn_timer.tv, &tv_now);</span><br><span> error_us = elapsed_us - FRAME_DURATION_uS;</span><br><span> #ifdef DEBUG_CLOCK</span><br><span style="color: hsl(0, 100%, 40%);">- printf("%s(): %09ld, elapsed_us=%05d, error_us=%-d: fn=%d\n", __func__,</span><br><span style="color: hsl(120, 100%, 40%);">+ printf("%s(): %09ld, elapsed_us=%05" PRId64 ", error_us=%-d: fn=%d\n", __func__,</span><br><span> tv_now.tv_nsec, elapsed_us, error_us, tcs->last_fn_timer.fn+1);</span><br><span> #endif</span><br><span> tcs->last_fn_timer.tv = tv_now;</span><br><span> </span><br><span> /* if someone played with clock, or if the process stalled */</span><br><span> if (elapsed_us > FRAME_DURATION_uS * MAX_FN_SKEW || elapsed_us < 0) {</span><br><span style="color: hsl(0, 100%, 40%);">- LOGP(DL1C, LOGL_ERROR, "PC clock skew: elapsed_us=%d, error_us=%d\n",</span><br><span style="color: hsl(120, 100%, 40%);">+ LOGP(DL1C, LOGL_ERROR, "PC clock skew: elapsed_us=%" PRId64 ", error_us=%" PRId64 "\n",</span><br><span> elapsed_us, error_us);</span><br><span> goto no_clock;</span><br><span> }</span><br><span>@@ -1591,8 +1590,8 @@</span><br><span> {</span><br><span> struct osmo_trx_clock_state *tcs = &g_clk_s;</span><br><span> struct timespec tv_now;</span><br><span style="color: hsl(0, 100%, 40%);">- int elapsed_us, elapsed_fn;</span><br><span style="color: hsl(0, 100%, 40%);">- int64_t elapsed_us_since_clk, elapsed_fn_since_clk, error_us_since_clk;</span><br><span style="color: hsl(120, 100%, 40%);">+ int elapsed_fn;</span><br><span style="color: hsl(120, 100%, 40%);">+ int64_t elapsed_us, elapsed_us_since_clk, elapsed_fn_since_clk, error_us_since_clk;</span><br><span> unsigned int fn_caught_up = 0;</span><br><span> const struct timespec interval = { .tv_sec = 0, .tv_nsec = FRAME_DURATION_nS };</span><br><span> </span><br><span>@@ -1655,7 +1654,7 @@</span><br><span> return trx_setup_clock(bts, tcs, &tv_now, &interval, fn);</span><br><span> }</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- LOGP(DL1C, LOGL_INFO, "GSM clock jitter: %d us (elapsed_fn=%d)\n",</span><br><span style="color: hsl(120, 100%, 40%);">+ LOGP(DL1C, LOGL_INFO, "GSM clock jitter: %" PRId64 "us (elapsed_fn=%d)\n",</span><br><span> elapsed_fn * FRAME_DURATION_uS - elapsed_us, elapsed_fn);</span><br><span> </span><br><span> /* too many frames have been processed already */</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/10488">change 10488</a>. 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<div style="display:none"> Gerrit-Project: osmo-bts </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-MessageType: newchange </div>
<div style="display:none"> Gerrit-Change-Id: Idfd9c807e35cd7fb5c80625b9746121f81c24599 </div>
<div style="display:none"> Gerrit-Change-Number: 10488 </div>
<div style="display:none"> Gerrit-PatchSet: 1 </div>
<div style="display:none"> Gerrit-Owner: Stefan Sperling <ssperling@sysmocom.de> </div>