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. > ``` > - 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>
