Switch to using timef instead of gettimeofday

This encapsulates the tricky arithmetic inside timef(), which uses
gettimeofday.

src/builtin_jobs.cpp

@@ -29,24 +29,13 @@ enum {
 /// Calculates the cpu usage (in percent) of the specified job.
 static int cpu_use(const job_t *j) {
     double u = 0;
-
     for (const process_ptr_t &p : j->processes) {
-        struct timeval t;
-        unsigned long jiffies;
-        gettimeofday(&t, nullptr);
-        jiffies = proc_get_jiffies(p->pid);
-
-        double t1 = 1000000.0 * p->last_time.tv_sec + p->last_time.tv_usec;
-        double t2 = 1000000.0 * t.tv_sec + t.tv_usec;
-
-        // Check for a race condition that can cause negative CPU usage to be reported (#7066)
-        unsigned long cached_last_jiffies = p->last_jiffies;
-        if (t2 < t1 || jiffies < cached_last_jiffies) {
-            continue;
+        timepoint_t now = timef();
+        unsigned long jiffies = proc_get_jiffies(p->pid);
+        double since = now - p->last_time;
+        if (since > 0 && jiffies > p->last_jiffies) {
+            u += (jiffies - p->last_jiffies) / since;
         }
-
-        // std::fwprintf( stderr, L"t1 %f t2 %f p1 %d p2 %d\n", t1, t2, jiffies, p->last_jiffies );
-        u += (static_cast<double>(jiffies - cached_last_jiffies)) / (t2 - t1);
     }
     return u * 1000000;
 }

src/common.cpp

@@ -1723,13 +1723,10 @@ void format_size_safe(char buff[128], unsigned long long sz) {
     }
 }
 
-/// Return the number of seconds from the UNIX epoch, with subsecond precision. This function uses
-/// the gettimeofday function and will have the same precision as that function.
 double timef() {
     struct timeval tv;
     assert_with_errno(gettimeofday(&tv, nullptr) != -1);
-    // return (double)tv.tv_sec + 0.000001 * tv.tv_usec;
-    return static_cast<double>(tv.tv_sec) + 1e-6 * tv.tv_usec;
+    return static_cast<timepoint_t>(tv.tv_sec) + 1e-6 * tv.tv_usec;
 }
 
 void exit_without_destructors(int code) { _exit(code); }

src/common.h

@@ -13,6 +13,7 @@
 
 #include <algorithm>
 #include <atomic>
+#include <cmath>
 #include <functional>
 #include <memory>
 #include <mutex>
@@ -516,7 +517,8 @@ void bugreport();
 
 /// Return the number of seconds from the UNIX epoch, with subsecond precision. This function uses
 /// the gettimeofday function and will have the same precision as that function.
-double timef();
+using timepoint_t = double;
+timepoint_t timef();
 
 /// Call the following function early in main to set the main thread. This is our replacement for
 /// pthread_main_np().

src/proc.cpp

@@ -765,7 +765,7 @@ unsigned long proc_get_jiffies(pid_t inpid) {
 void proc_update_jiffies(parser_t &parser) {
     for (const auto &job : parser.jobs()) {
         for (process_ptr_t &p : job->processes) {
-            gettimeofday(&p->last_time, nullptr);
+            p->last_time = timef();
             p->last_jiffies = proc_get_jiffies(p->pid);
         }
     }

src/proc.h

@@ -277,8 +277,8 @@ class process_t : noncopyable_t {
     /// Reported status value.
     proc_status_t status{};
 
-    /// Last time of cpu time check.
-    struct timeval last_time {};
+    /// Last time of cpu time check, in seconds (per timef).
+    timepoint_t last_time{0};
 
     /// Number of jiffies spent in process at last cpu time check.
     unsigned long last_jiffies{0};

src/reader.cpp

@@ -2408,23 +2408,9 @@ void reader_data_t::set_buffer_maintaining_pager(const wcstring &b, size_t pos,
     history_search.reset();
 }
 
-static void set_env_cmd_duration(struct timeval *after, struct timeval *before, env_stack_t &vars) {
-    time_t secs = after->tv_sec - before->tv_sec;
-    suseconds_t usecs = after->tv_usec - before->tv_usec;
-
-    if (after->tv_usec < before->tv_usec) {
-        usecs += 1000000;
-        secs -= 1;
-    }
-
-    vars.set_one(ENV_CMD_DURATION, ENV_UNEXPORT, std::to_wstring((secs * 1000) + (usecs / 1000)));
-}
-
 /// Run the specified command with the correct terminal modes, and while taking care to perform job
 /// notification, set the title, etc.
 static eval_res_t reader_run_command(parser_t &parser, const wcstring &cmd) {
-    struct timeval time_before, time_after;
-
     wcstring ft = tok_command(cmd);
 
     // For compatibility with fish 2.0's $_, now replaced with `status current-command`
@@ -2435,16 +2421,18 @@ static eval_res_t reader_run_command(parser_t &parser, const wcstring &cmd) {
     outp.set_color(rgb_color_t::normal(), rgb_color_t::normal());
     term_donate();
 
-    gettimeofday(&time_before, nullptr);
-
+    timepoint_t time_before = timef();
     auto eval_res = parser.eval(cmd, io_chain_t{});
     job_reap(parser, true);
 
-    gettimeofday(&time_after, nullptr);
-
     // update the execution duration iff a command is requested for execution
     // issue - #4926
-    if (!ft.empty()) set_env_cmd_duration(&time_after, &time_before, parser.vars());
+    if (!ft.empty()) {
+        timepoint_t time_after = timef();
+        double duration = time_after - time_before;
+        long duration_ms = std::round(duration * 1000);
+        parser.vars().set_one(ENV_CMD_DURATION, ENV_UNEXPORT, to_string(duration_ms));
+    }
 
     term_steal();