> From: Thomas Monjalon [mailto:tho...@monjalon.net] > Sent: Wednesday, May 5, 2021 8:51 AM > > 05/05/2021 08:26, Morten Brørup: > > > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Thomas > Monjalon > > > Sent: Wednesday, May 5, 2021 8:14 AM > > > > > > 04/05/2021 21:12, Morten Brørup: > > > > > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Thomas > > > Monjalon > > > > > Sent: Tuesday, May 4, 2021 6:50 PM > > > > > > > > > > 29/04/2021 04:10, Min Hu (Connor): > > > > > > Currently, the mp uses gettimeofday() API to get the time, > and > > > used > > > > > as > > > > > > timeout parameter. > > > > > > > > > > > > But the time which gets from gettimeofday() API isn't > > > monotonically > > > > > > increasing. The process may fail if the system time is > changed. > > > > > > > > > > > > This fixes it by using clock_gettime() API with monotonic > > > > > attribution. > > > > > > > > > > > > Fixes: 783b6e54971d ("eal: add synchronous multi-process > > > > > communication") > > > > > > Fixes: f05e26051c15 ("eal: add IPC asynchronous request") > > > > > > Cc: sta...@dpdk.org > > > > > > > > > > > > Signed-off-by: Chengwen Feng <fengcheng...@huawei.com> > > > > > > Signed-off-by: Min Hu (Connor) <humi...@huawei.com> > > > > > > --- > > > > > [...] > > > > > > --- a/lib/eal/common/eal_common_proc.c > > > > > > +++ b/lib/eal/common/eal_common_proc.c > > > > > > - if (gettimeofday(&now, NULL) < 0) { > > > > > > - RTE_LOG(ERR, EAL, "Cannot get current time\n"); > > > > > > - goto no_trigger; > > > > > > - } > > > > > > - ts_now.tv_nsec = now.tv_usec * 1000; > > > > > > - ts_now.tv_sec = now.tv_sec; > > > > > > + clock_gettime(CLOCK_MONOTONIC, &ts_now); > > > > > > > > > > Why not testing the return value? > > > > > > > > Because it is guaranteed not to fail. Ref: > > > > https://linux.die.net/man/3/clock_gettime > > > > https://www.freebsd.org/cgi/man.cgi?query=clock_gettime > > > > > > I see "return 0 for success, or -1 for failure". > > > Where is it said it cannot fail? > > > > I'm sorry about being unclear. Referring to the "Errors" chapter in > the function's man page, this function call is guaranteed not to fail > with these parameters. So there is no need to check the return value. > > I don't agree. > Especially for this error: > "The clk_id specified is not supported on this system." > How can you be sure it is always supported for any system > we try to run this code now and in future experiments? >
I referred to both Linux and BSD man pages because they say that it is defined there. This should cover current supported systems, excl. Windows, which doesn't have gettimeofday() or clock_gettime() anyway. However, for future operating systems that might be supported by DPDK, you are correct that CLOCK_MONOTONIC is optional. Ref: https://pubs.opengroup.org/onlinepubs/009695399/basedefs/time.h.html This can be fixed by adding: #if !defined(CLOCK_MONOTONIC) #error CLOCK_MONOTONIC is not defined. #endif If we only check the return value at runtime, the function would fail every time on a system without CLOCK_MONOTONIC, and eal_common_proc.c would need to be fixed anyway. It's better to catch at compile time.
