From d89523644308afd24d47ca3dcf4098d0a719e919 Mon Sep 17 00:00:00 2001 From: Eric van Gyzen Date: Thu, 27 May 2021 11:33:22 -0500 Subject: [PATCH] libprocstat kstack: fix race with thread creation When collecting kernel stacks for a target process, if the process adds a thread between the two calls to sysctl, ignore the additional threads. Previously, procstat would print only a useless error message. Now, it prints a consistent snapshot of the stacks. We know that snapshot is already stale, but it could still be stale even with a more complex fix to reallocate and retry, so such a fix is hardly worth the effort. Reported by: Daniel.Mitchell@emc.com MFC after: 1 week Sponsored by: Dell EMC Isilon (cherry picked from commit 427f12f150e875c40acb84f292a80bfa0b90a1a2) --- lib/libprocstat/libprocstat.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/libprocstat/libprocstat.c b/lib/libprocstat/libprocstat.c index 89896a81388..9409fb0e196 100644 --- a/lib/libprocstat/libprocstat.c +++ b/lib/libprocstat/libprocstat.c @@ -2610,7 +2610,8 @@ procstat_getkstack_sysctl(pid_t pid, int *cntp) warn("malloc(%zu)", len); return (NULL); } - if (sysctl(name, nitems(name), kkstp, &len, NULL, 0) == -1) { + if (sysctl(name, nitems(name), kkstp, &len, NULL, 0) == -1 && + errno != ENOMEM) { warn("sysctl: kern.proc.pid: %d", pid); free(kkstp); return (NULL);