On Thu, Mar 6, 2025, 3:35 AM Mateusz Guzik <mjgu...@gmail.com> wrote:
> On Thu, Mar 6, 2025 at 12:32 PM Zhenlei Huang <z...@freebsd.org> wrote: > > > > > > > > On Mar 6, 2025, at 7:03 PM, Mateusz Guzik <m...@freebsd.org> wrote: > > > > The branch main has been updated by mjg: > > > > URL: > https://cgit.FreeBSD.org/src/commit/?id=234683726708cf5212d672d676d30056d4133859 > > > > commit 234683726708cf5212d672d676d30056d4133859 > > Author: Mateusz Guzik <m...@freebsd.org> > > AuthorDate: 2025-03-06 11:01:49 +0000 > > Commit: Mateusz Guzik <m...@freebsd.org> > > CommitDate: 2025-03-06 11:01:49 +0000 > > > > devclass: make devclass_alloc_unit use M_NOWAIT > > > > The only caller already does this. > > > > The routine can be called with a mutex held making M_WAITOK illegal. > > > > Sponsored by: Rubicon Communications, LLC ("Netgate") > > --- > > sys/kern/subr_bus.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c > > index 9506e471705c..0422352bba51 100644 > > --- a/sys/kern/subr_bus.c > > +++ b/sys/kern/subr_bus.c > > @@ -1208,6 +1208,7 @@ devclass_get_sysctl_tree(devclass_t dc) > > static int > > devclass_alloc_unit(devclass_t dc, device_t dev, int *unitp) > > { > > + device_t *devices; > > const char *s; > > int unit = *unitp; > > > > @@ -1264,8 +1265,11 @@ devclass_alloc_unit(devclass_t dc, device_t dev, > int *unitp) > > int newsize; > > > > newsize = unit + 1; > > - dc->devices = reallocf(dc->devices, > > - newsize * sizeof(*dc->devices), M_BUS, M_WAITOK); > > + devices = reallocf(dc->devices, > > + newsize * sizeof(*dc->devices), M_BUS, M_NOWAIT); > > > > > > I'd recommend against this. From the commit message of f3d3c63442ff, > Warner said, > > > In addition, transition to M_WAITOK since this is a sleepable context > > So, the M_WAITOK is intentional. > > > > Rather than reverting this, the caller devclass_add_device() should use > M_WAITOK. > > > > Per my commit message this is callable from a *NOT* sleepable context. > > Here is a splat we got at Netgate: > > uma_zalloc_debug: zone "malloc-16" with the following non-sleepable locks > held: > exclusive sleep mutex SD slot mtx (sdhci) r = 0 (0xd8dec028) locked @ > > /var/jenkins/workspace/pfSense-Plus-snapshots-25_03-main/sources/FreeBSD-src-plus-RELENG_25_03/sys/dev/sdhci/sdhci.c:688 > stack backtrace: > #0 0xc0330ebc at witness_debugger+0x78 > #1 0xc033217c at witness_warn+0x428 > #2 0xc05b0a58 at uma_zalloc_debug+0x34 > #3 0xc05b067c at uma_zalloc_arg+0x30 > #4 0xc0291760 at malloc+0x8c > #5 0xc02920ec at reallocf+0x14 > #6 0xc02f8894 at devclass_add_device+0x1e8 > #7 0xc02f6c78 at make_device+0xe0 > #8 0xc02f6abc at device_add_child_ordered+0x30 > #9 0xc0156e0c at sdhci_card_task+0x238 > #10 0xc0324090 at taskqueue_run_locked+0x1b4 > #11 0xc0323ea0 at taskqueue_run+0x50 > #12 0xc0275f88 at ithread_loop+0x264 > #13 0xc0271f28 at fork_exit+0xa0 > #14 0xc05f82d4 at swi_exit+0 > > It may be some callers are sleepable. Perhaps a different variant > accepting flags would be prudent, but I have no interest in looking > into that. > This is a big in sdhci_card_task. Newbus in general isn't callable from a sleepable context. Warner > ``` > > - dev->nameunit = malloc(buflen, M_BUS, M_NOWAIT|M_ZERO); > > - if (!dev->nameunit) > > - return (ENOMEM); > > + dev->nameunit = malloc(buflen, M_BUS, M_WAITOK | M_ZERO); > > ``` > > > > Best regards, > > Zhenlei > > > > + if (devices == NULL) > > + return (ENOMEM); > > + dc->devices = devices; > > memset(dc->devices + dc->maxunit, 0, > > sizeof(device_t) * (newsize - dc->maxunit)); > > dc->maxunit = newsize; > > > > > > > > > > > -- > Mateusz Guzik <mjguzik gmail.com> >
