Thanks :) yeah, first kernel patch. I got pretty annoyed by how long I spent trying to figure out why my database was reporting disk space errors on pthread_create, and when I finally worked out what was going on sending a patch to fix it was somewhat therapeutic!
On Tue, Sep 4, 2018 at 9:22 AM Andrew Morton <[email protected]> wrote: > > On Mon, 3 Sep 2018 04:10:16 -0700 [email protected] wrote: > > > From: KJ Tsanaktsidis <[email protected]> > > > > Make the clone and fork syscalls return EAGAIN when the limit on the > > number of pids /proc/sys/kernel/pid_max is exceeded. > > > > Currently, when the pid_max limit is exceeded, the kernel will return > > ENOSPC from the fork and clone syscalls. This is contrary to the > > documented behaviour, which explicitly calls out the pid_max case as one > > where EAGAIN should be returned. It also leads to really confusing error > > messages in userspace programs which will complain about a lack of disk > > space when they fail to create processes/threads for this reason. > > > > This error is being returned because the alloc_pid function uses the idr > > api to find a new pid; when there are none available, idr_alloc_cyclic > > is returns -ENOSPC, and this is being propagated back into userspace. > > > > This behaviour has been broken before, and was explicitly fixed in > > commit 35f71bc0a09a ("fork: report pid reservation failure properly"), > > so I think -EAGAIN is definitely the right thing to return in this case. > > The current behaviour change dates from commit 95846ecf9dac ("pid: > > replace pid bitmap implementation with IDR AIP") and was I believe > > unintentional. > > > > This patch has no impact on the case where allocating a pid fails > > because the child reaper for the namespace is dead; that case will still > > return -ENOMEM. > > Thanks. First ever kernel patch? It was a damn good one! > > > Fixes: 95846ecf9dac ("pid: replace pid bitmap implementation with IDR AIP") > > Signed-off-by: KJ Tsanaktsidis <[email protected]> > > I'll add cc:stable here so the fix gets backported into earlier kernels >
