Date: Mon, 13 Jun 2022 19:33:29 GMT From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 02a2aacbe2c8 - main - issignal(): ignore signals when process is single-threading for exit Message-ID: <202206131933.25DJXTwW023532@gitrepo.freebsd.org>
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The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=02a2aacbe2c81be455811fa9d4200101f70a86d2 commit 02a2aacbe2c81be455811fa9d4200101f70a86d2 Author: Konstantin Belousov <kib@FreeBSD.org> AuthorDate: 2022-05-26 19:18:57 +0000 Commit: Konstantin Belousov <kib@FreeBSD.org> CommitDate: 2022-06-13 19:30:02 +0000 issignal(): ignore signals when process is single-threading for exit Places that will wait for curproc->p_singlethr to become zero (in the next commit, the counter of number of external single-threading is to be introduced), must wait for it interruptible, otherwise we deadlock. On the other hand, a signal delivered during this window, if directed to the waiting thread, would cause the wait loop to become a busy loop. Since we are exiting, it is safe to ignore the signals. Reviewed by: markj Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D35310 --- sys/kern/kern_sig.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c index afb2fd78c231..e3bbbd23ae6c 100644 --- a/sys/kern/kern_sig.c +++ b/sys/kern/kern_sig.c @@ -2928,7 +2928,7 @@ sigprocess(struct thread *td, int sig) /* * We should allow pending but ignored signals below - * only if there is sigwait() active, or P_TRACED was + * if there is sigwait() active, or P_TRACED was * on when they were posted. */ if (SIGISMEMBER(ps->ps_sigignore, sig) && @@ -2937,6 +2937,16 @@ sigprocess(struct thread *td, int sig) return (SIGSTATUS_IGNORE); } + /* + * If the process is going to single-thread mode to prepare + * for exit, there is no sense in delivering any signal + * to usermode. Another important consequence is that + * msleep(..., PCATCH, ...) now is only interruptible by a + * suspend request. + */ + if ((p->p_flag2 & P2_WEXIT) != 0) + return (SIGSTATUS_IGNORE); + if ((p->p_flag & (P_TRACED | P_PPTRACE)) == P_TRACED) { /* * If traced, always stop.
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