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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |EXAMPLE |FILES |SEE ALSO |AUTHOR |REPORTING BUGS |LICENSE |RESOURCES |COPYING |NOTES |COLOPHON | |
LIBTRACEFS(3) libtracefs ManualLIBTRACEFS(3)tracefs_find_cid_pid, tracefs_instance_find_cid_pid, tracefs_time_conversion - helper functions to handle tracing guests
#include <tracefs.h> char *tracefs_find_cid_pid(intcid); char *tracefs_instance_find_cid_pid(struct tracefs_instance *instance, intcid); inttracefs_time_conversion(intcpu, int *shift, int *multi, long long *offset);
Thetracefs_find_cid_pid() will use tracing to follow the wakeups of connecting to the givencid in order to find the pid of the guest thread that belongs to the vsocket cid. It will then read the proc file system to find the thread leader, and it will return the pid of the thread leader. Thetracefs_instance_find_cid_pid() is the same astracefs_find_cid_pid() but defines the instance to use to perform the tracing in. If NULL it will use the top level buffer to perform the tracing. Thetracefs_time_conversion() will return the values used by the kernel to convert the raw time stamp counter into nanoseconds for the givencpu. Pointers forshift,multi andoffset can be NULL to be ignored, otherwise they are set with the shift, multiplier and offset repectively.
Bothtracefs_find_cid_pid() andtracefs_instance_find_cid_pid() will return the pid of the guest main thread that belongs to thecid, or -1 on error (or not found).
#include <stdlib.h> #include <unistd.h> #include <tracefs.h> #define MAX_CID 256 static void find_cid(struct tracefs_instance *instance, int cid) { int pid; pid = tracefs_instance_find_cid_pid(instance, cid); if (pid >= 0) printf("%d\t%d\n", cid, pid); } static int find_cids(void) { struct tracefs_instance *instance; char *name; int cid; int ret; ret = asprintf(&name, "vsock_find-%d\n", getpid()); if (ret < 0) return ret; instance = tracefs_instance_create(name); free(name); if (!instance) return -1; for (cid = 0; cid < MAX_CID; cid++) find_cid(instance, cid); tracefs_event_disable(instance, NULL, NULL); tracefs_instance_destroy(instance); tracefs_instance_free(instance); return 0; } struct time_info { int shift; int multi; }; static void show_time_conversion(void) { struct time_info *tinfo; int cpus; int cpu; int ret; cpus = sysconf(_SC_NPROCESSORS_CONF); tinfo = calloc(cpus, sizeof(*tinfo)); if (!tinfo) exit(-1); for (cpu = 0; cpu < cpus; cpu++) { ret = tracefs_time_conversion(cpu, &tinfo[cpu].shift, &tinfo[cpu].multi, NULL); if (ret) break; } if (cpu != cpus) { if (!cpu) { perror("tracefs_time_conversion"); exit(-1); } printf("Only read %d of %d CPUs", cpu, cpus); cpus = cpu + 1; } /* Check if all the shift and mult values are the same */ for (cpu = 1; cpu < cpus; cpu++) { if (tinfo[cpu - 1].shift != tinfo[cpu].shift) break; if (tinfo[cpu - 1].multi != tinfo[cpu].multi) break; } if (cpu == cpus) { printf("All cpus have:\n"); printf(" shift: %d\n", tinfo[0].shift); printf(" multi: %d\n", tinfo[0].multi); printf("\n"); return; } for (cpu = 0; cpu < cpus; cpu++) { printf("CPU: %d\n", cpu); printf(" shift: %d\n", tinfo[cpu].shift); printf(" multi: %d\n", tinfo[cpu].multi); printf("\n"); } } int main(int argc, char *argv[]) { show_time_conversion(); find_cids(); exit(0); }tracefs.h Header file to include in order to have access to the library APIs.-ltracefs Linker switch to add when building a program that uses the library.
libtracefs(3),libtraceevent(3),trace-cmd(1)
Steven Rostedt<rostedt@goodmis.org[1]>Tzvetomir Stoyanov<tz.stoyanov@gmail.com[2]>
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).
1. rostedt@goodmis.org mailto:rostedt@goodmis.org 2. tz.stoyanov@gmail.com mailto:tz.stoyanov@gmail.com 3. linux-trace-devel@vger.kernel.org mailto:linux-trace-devel@vger.kernel.org
This page is part of thelibtracefs (Linux kernel trace file system library) project. Information about the project can be found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report for this manual page, see ⟨https://www.trace-cmd.org/⟩. This page was obtained from the project's upstream Git repository ⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-06-02.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orglibtracefs 1.7.0 12/22/2023LIBTRACEFS(3)HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |