| Message ID | 20240515183033.97232-1-james.hilliard1@gmail.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [1/1] suricatta: prefer CLOCK_MONOTONIC for suricatta_wait | expand |
Hi James, On 15.05.24 20:30, James Hilliard wrote: > When calling sem_timedwait there may be side effects caused by > discontinuous jumps in the system time which can cause the clock > to go backwards. > > To try and avoid side effects caused by these issues use the new > sem_clockwait function with CLOCK_MONOTONIC which should be available > on linux as of glibc version 2.30. Other libc's do not appear to have > support for sem_clockwait so we still have to fall back to > sem_timedwait on those systems. > > Signed-off-by: James Hilliard <james.hilliard1@gmail.com> > --- > suricatta/suricatta.c | 27 +++++++++++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-) > > diff --git a/suricatta/suricatta.c b/suricatta/suricatta.c > index 20eb427f..39798a6d 100644 > --- a/suricatta/suricatta.c > +++ b/suricatta/suricatta.c > @@ -25,6 +25,16 @@ > #include "swupdate_settings.h" > #include <network_ipc.h> > > +/* > + * Needs sem_clockwait which was added in glibc v2.30 on linux. > + */ > +#if defined(__linux__) && defined(__GLIBC__) && \ > + (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30)) > +#define USE_SEM_MONOTONIC 1 > +#else > +#define USE_SEM_MONOTONIC 0 > +#endif > + > static bool enable = true; > static bool trigger = false; > static struct option long_options[] = { > @@ -185,12 +195,20 @@ int suricatta_wait(int seconds) > int retval; > int enable_entry = enable; > > +#if USE_SEM_MONOTONIC > + clock_gettime(CLOCK_MONOTONIC, &tp); > +#else > clock_gettime(CLOCK_REALTIME, &tp); > - int t_entry = tp.tv_sec; > +#endif > + time_t t_entry = tp.tv_sec; > > tp.tv_sec += seconds; > DEBUG("Sleeping for %d seconds.", seconds); > +#if USE_SEM_MONOTONIC > + retval = sem_clockwait(&suricatta_enable_sema, CLOCK_MONOTONIC, &tp); > +#else > retval = sem_timedwait(&suricatta_enable_sema, &tp); > +#endif > > if (retval) { > if (errno != ETIMEDOUT) { > @@ -200,7 +218,12 @@ int suricatta_wait(int seconds) > /* else: Suricatta awakened because timeout expired */ > } else { > /* suricatta_enable_sema unlocked */ > - time_t t_wake = time(NULL); > +#if USE_SEM_MONOTONIC > + clock_gettime(CLOCK_MONOTONIC, &tp); > +#else > + clock_gettime(CLOCK_REALTIME, &tp); > +#endif > + time_t t_wake = tp.tv_sec; > > TRACE("Suricatta woke up for IPC at %ld seconds", t_wake - t_entry); > /* Applied to -master, thanks ! Best regards, Stefano Babic
diff --git a/suricatta/suricatta.c b/suricatta/suricatta.c index 20eb427f..39798a6d 100644 --- a/suricatta/suricatta.c +++ b/suricatta/suricatta.c @@ -25,6 +25,16 @@ #include "swupdate_settings.h" #include <network_ipc.h> +/* + * Needs sem_clockwait which was added in glibc v2.30 on linux. + */ +#if defined(__linux__) && defined(__GLIBC__) && \ + (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30)) +#define USE_SEM_MONOTONIC 1 +#else +#define USE_SEM_MONOTONIC 0 +#endif + static bool enable = true; static bool trigger = false; static struct option long_options[] = { @@ -185,12 +195,20 @@ int suricatta_wait(int seconds) int retval; int enable_entry = enable; +#if USE_SEM_MONOTONIC + clock_gettime(CLOCK_MONOTONIC, &tp); +#else clock_gettime(CLOCK_REALTIME, &tp); - int t_entry = tp.tv_sec; +#endif + time_t t_entry = tp.tv_sec; tp.tv_sec += seconds; DEBUG("Sleeping for %d seconds.", seconds); +#if USE_SEM_MONOTONIC + retval = sem_clockwait(&suricatta_enable_sema, CLOCK_MONOTONIC, &tp); +#else retval = sem_timedwait(&suricatta_enable_sema, &tp); +#endif if (retval) { if (errno != ETIMEDOUT) { @@ -200,7 +218,12 @@ int suricatta_wait(int seconds) /* else: Suricatta awakened because timeout expired */ } else { /* suricatta_enable_sema unlocked */ - time_t t_wake = time(NULL); +#if USE_SEM_MONOTONIC + clock_gettime(CLOCK_MONOTONIC, &tp); +#else + clock_gettime(CLOCK_REALTIME, &tp); +#endif + time_t t_wake = tp.tv_sec; TRACE("Suricatta woke up for IPC at %ld seconds", t_wake - t_entry); /*
When calling sem_timedwait there may be side effects caused by discontinuous jumps in the system time which can cause the clock to go backwards. To try and avoid side effects caused by these issues use the new sem_clockwait function with CLOCK_MONOTONIC which should be available on linux as of glibc version 2.30. Other libc's do not appear to have support for sem_clockwait so we still have to fall back to sem_timedwait on those systems. Signed-off-by: James Hilliard <james.hilliard1@gmail.com> --- suricatta/suricatta.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-)