> Le 8 avr. 2021 à 21:26, Simon Marchi a écrit : > > Can you please explain in the commit message what harm > that wait4 call does and why we want to remove it? In trying to make a better case in the commit message, I found that swapping the two patches around made more sense. Here is an updated, rebased, single patch (working under the assumption that the other two will be merged first): From 5c3756e9eb0342b1a5a23bcb54d5b8317743ce0d Mon Sep 17 00:00:00 2001 From: Dominique Quatravaux Date: Thu, 8 Apr 2021 21:35:57 +0200 Subject: [PATCH] [delete] not-so-harmless spurious call to `wait4` MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit As seen in https://sourceware.org/bugzilla/show_bug.cgi?id=24069 this code will typically wait4() a second time on the same process that was already wait4()'d a few lines above. While this used to be harmless/idempotent (when we assumed that the process already exited), this now causes a deadlock in the WIFSTOPPED case. The early (~2019) history of bug #24069 cautiously suggests to use WNOHANG instead of outright deleting the call. However, tests on the current version of Darwin (Big Sur) demonstrate that gdb runs just fine without a redundant call to wait4(), as would be expected. Notwithstanding the debatable value of conserving bug compatibility with an OS release that is more than a decade old, there is scant evidence of what that double-wait4() was supposed to achieve in the first place - A cursory investigation with `git blame` pinpoints commits bb00b29d7802 and a80b95ba67e2 from the 2008-2009 era, but fails to answer the “why” question conclusively. --- gdb/darwin-nat.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/gdb/darwin-nat.c b/gdb/darwin-nat.c index d3edcdf3a74..ac19d330ffb 100644 --- a/gdb/darwin-nat.c +++ b/gdb/darwin-nat.c @@ -1113,9 +1113,6 @@ darwin_nat_target::decode_message (mach_msg_header_t *hdr, res_pid, status->value.sig); } - /* Looks necessary on Leopard and harmless... */ - wait4 (inf->pid, &wstatus, 0, NULL); - return ptid_t (inf->pid); } else -- 2.31.1 — Dominique Quatravaux +41 21 69 35624