Date: Wed, 7 Sep 2022 11:36:03 +0200 From: Mateusz Guzik <mjguzik@gmail.com> To: Konstantin Belousov <kostikbel@gmail.com> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 69413598d266 - main - signal: use proc_iterate to save on work Message-ID: <CAGudoHFHSGkqDxApAPaMtJYPSdgaUKFbJRfCbpb0mWOcC4v47g@mail.gmail.com> In-Reply-To: <YxhiKyBFN0U1oabr@kib.kiev.ua> References: <202209051156.285BuFWK076782@gitrepo.freebsd.org> <YxXoozljiIUtDUn7@kib.kiev.ua> <CAGudoHGMQh0S%2BSv_wYjgrG=u9J1C_GkrQ3_rPpeSN%2Bj%2B_n9tgw@mail.gmail.com> <YxhiKyBFN0U1oabr@kib.kiev.ua>
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On 9/7/22, Konstantin Belousov <kostikbel@gmail.com> wrote: > On Mon, Sep 05, 2022 at 06:07:08PM +0200, Mateusz Guzik wrote: >> On 9/5/22, Konstantin Belousov <kostikbel@gmail.com> wrote: >> > On Mon, Sep 05, 2022 at 11:56:15AM +0000, Mateusz Guzik wrote: >> >> The branch main has been updated by mjg: >> >> >> >> URL: >> >> https://cgit.FreeBSD.org/src/commit/?id=69413598d2660054e29cac9454fe18c08e3bf36d >> >> >> >> commit 69413598d2660054e29cac9454fe18c08e3bf36d >> >> Author: Mateusz Guzik <mjg@FreeBSD.org> >> >> AuthorDate: 2022-03-10 18:58:12 +0000 >> >> Commit: Mateusz Guzik <mjg@FreeBSD.org> >> >> CommitDate: 2022-09-05 11:54:47 +0000 >> >> >> >> signal: use proc_iterate to save on work >> >> >> >> Most notably poudriere performs kill -9 -1 in jails for each port >> >> being built. This reduces the scan from hundrends of processes to >> >> literally 1. >> >> >> >> Reviewed by: jamie, markj >> >> Differential Revision: https://reviews.freebsd.org/D34522 >> >> --- >> >> sys/kern/kern_sig.c | 39 ++++++++++++++++++++++++++++----------- >> >> 1 file changed, 28 insertions(+), 11 deletions(-) >> >> >> >> diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c >> >> index 6fd3eca0a14e..c50a37de07e6 100644 >> >> --- a/sys/kern/kern_sig.c >> >> +++ b/sys/kern/kern_sig.c >> >> @@ -1776,18 +1776,13 @@ struct killpg1_ctx { >> >> }; >> >> >> >> static void >> >> -killpg1_sendsig(struct proc *p, bool notself, struct killpg1_ctx >> >> *arg) >> >> +killpg1_sendsig_locked(struct proc *p, struct killpg1_ctx *arg) >> >> { >> >> int err; >> >> >> >> - if (p->p_pid <= 1 || (p->p_flag & P_SYSTEM) != 0 || >> >> - (notself && p == arg->td->td_proc) || p->p_state == PRS_NEW) >> >> - return; >> >> - PROC_LOCK(p); >> >> err = p_cansignal(arg->td, p, arg->sig); >> >> if (err == 0 && arg->sig != 0) >> >> pksignal(p, arg->sig, arg->ksi); >> >> - PROC_UNLOCK(p); >> >> if (err != ESRCH) >> >> arg->found = true; >> >> if (err == 0) >> >> @@ -1796,6 +1791,31 @@ killpg1_sendsig(struct proc *p, bool notself, >> >> struct killpg1_ctx *arg) >> >> arg->ret = err; >> >> } >> >> >> >> +static void >> >> +killpg1_sendsig(struct proc *p, bool notself, struct killpg1_ctx >> >> *arg) >> >> +{ >> >> + >> >> + if (p->p_pid <= 1 || (p->p_flag & P_SYSTEM) != 0 || >> >> + (notself && p == arg->td->td_proc) || p->p_state == PRS_NEW) >> >> + return; >> >> + >> >> + PROC_LOCK(p); >> >> + killpg1_sendsig_locked(p, arg); >> >> + PROC_UNLOCK(p); >> >> +} >> >> + >> >> +static void >> >> +kill_processes_prison_cb(struct proc *p, void *arg) >> >> +{ >> >> + struct killpg1_ctx *ctx = arg; >> >> + >> >> + if (p->p_pid <= 1 || (p->p_flag & P_SYSTEM) != 0 || >> >> + (p == ctx->td->td_proc) || p->p_state == PRS_NEW) >> > Extra () >> > >> >> + return; >> >> + >> >> + killpg1_sendsig_locked(p, ctx); >> >> +} >> >> + >> >> /* >> >> * Common code for kill process group/broadcast kill. >> >> * cp is calling process. >> >> @@ -1817,11 +1837,8 @@ killpg1(struct thread *td, int sig, int pgid, >> >> int >> >> all, ksiginfo_t *ksi) >> >> /* >> >> * broadcast >> >> */ >> >> - sx_slock(&allproc_lock); >> >> - FOREACH_PROC_IN_SYSTEM(p) { >> >> - killpg1_sendsig(p, true, &arg); >> >> - } >> >> - sx_sunlock(&allproc_lock); >> >> + prison_proc_iterate(td->td_ucred->cr_prison, >> >> + kill_processes_prison_cb, &arg); >> >> } else { >> >> sx_slock(&proctree_lock); >> >> if (pgid == 0) { >> > >> > I believe before your change, kill(-1) would kill all processes in the >> > jail, which includes all processes in the nested jails. Now, it seems >> > that linkage prevents iterating over the nested jails, am I missing it? >> > >> >> See the pr_childcount check. If any jails pop up, there is a full scan >> like right now. And if the count transitions 0 -> 1 -> 0 during the >> iteration of the loop, there is nobody left to signal. > I see. > >> >> All previously existing races remain unaffected. > No, now you are potentially signalling some processes more than once. > Sending the signal is not idempotent operation. > You have a point, I was pretty fixated on just kill -9 -1. I'm going going to have to ponder a little bit, perhaps it is time to finally fix the races. -- Mateusz Guzik <mjguzik gmail.com>
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