git: 70cdab054c8f - stable/12 - rctl(4): support throttling resource usage to 0

[Jason A. Harmening]

The branch stable/12 has been updated by jah:

URL: https://cgit.FreeBSD.org/src/commit/?id=70cdab054c8ffe7f5561ab8f31db33ee62d12c9c

commit 70cdab054c8ffe7f5561ab8f31db33ee62d12c9c
Author:     Jason A. Harmening <jah at FreeBSD.org>
AuthorDate: 2020-12-30 23:29:44 +0000
Commit:     Jason A. Harmening <jah at FreeBSD.org>
CommitDate: 2021-01-26 03:57:44 +0000

    rctl(4): support throttling resource usage to 0
    
    For rate-based resources that support throttling (e.g.
    readiops/writeips), this fixes a divide-by-zero panic when rctl(8)
    passes 0 as the throttle value.  For these resources, treat
    zero-throttle requests as requests to suspend forward progress as long
    as possible using the duration specified in
    kern.racct.rctl.throttle_max.
    
    PR:             251803
    Reported by:    chris at cretaforce.gr
    
    (cherry picked from commit e8a5a1ad7154dc34e3a5234267e19faa86d5ff33)
---
 sys/kern/kern_rctl.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sys/kern/kern_rctl.c b/sys/kern/kern_rctl.c
index d79192927b54..138f73eabb21 100644
--- a/sys/kern/kern_rctl.c
+++ b/sys/kern/kern_rctl.c
@@ -596,6 +596,11 @@ rctl_enforce(struct proc *p, int resource, uint64_t amount)
 			if (p->p_state != PRS_NORMAL)
 				continue;
 
+			if (rule->rr_amount == 0) {
+				racct_proc_throttle(p, rctl_throttle_max);
+				continue;
+			}
+
 			/*
 			 * Make the process sleep for a fraction of second
 			 * proportional to the ratio of process' resource