KASSERT_WARN for asserting malloc(M_WAITOK) not in a non-sleepable thread

[Bryan Drewery]

Hi,

I've placed 2 reviews out in relation to
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=193696:

Add KASSERT_WARN which will work just like KASSERT except that no panic
will occur.  My own expectation would be that any use of it would
eventually be promoted to a full KASSERT.  It would only be used where
the impact is not known yet on all hardware/devices.  We don't want to
go adding a KASSERT and break boot for a whole class of systems.

  https://reviews.freebsd.org/D829 - KASSERT_WARN


Add the KASSERT_WARN to malloc(9) and uma_zalloc_arg(9) to ensure they
are not called from a non-sleepable thread.  This is currently violated
by cam, namely xpt_done_td() [see bug 193696].

  https://reviews.freebsd.org/D830 - Use KASSERT_WARN in malloc(9) and
uma_zalloc_arg(9)

One flaw of this is that the KASSERT_WARN in malloc(9) is called, prints
to console, continues, and then the uma_zalloc_arg(9) is called and does
the same.  I thought perhaps the KASSERT_WARN could only be added in
uma_zalloc_arg(9) for now and later the full KASSERT could be added in
malloc(9), but I think this could miss some cases for memguard and maybe
redzone uses.

By the way, it was mentioned to me that the interrupt assert may be
wrong but from my understanding the thread is in an interrupt context if
td_intr_nesting_level>0, so the check seems fine to me.

Example output:

> ada3: <Hitachi HDT721010SLA360 ST6OA31B> s/n STF605MH1THSXW detached
> KASSERT failed: malloc(M_WAITOK) in no_sleeping context
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe349829a340
> kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe349829a3f0
> _kassert_panic() at _kassert_panic+0xd7/frame 0xfffffe349829a470
> malloc() at malloc+0x2e4/frame 0xfffffe349829a4c0
> g_post_event_x() at g_post_event_x+0x84/frame 0xfffffe349829a510
> g_post_event() at g_post_event+0x5d/frame 0xfffffe349829a580
> adacleanup() at adacleanup+0x62/frame 0xfffffe349829a5a0
> cam_periph_release_locked_buses() at cam_periph_release_locked_buses+0xde/frame 0xfffffe349829aaa0
> cam_periph_release_locked() at cam_periph_release_locked+0x1b/frame 0xfffffe349829aac0
> adadone() at adadone+0x26e/frame 0xfffffe349829ab20
> xpt_done_process() at xpt_done_process+0x3a4/frame 0xfffffe349829ab60
> xpt_done_td() at xpt_done_td+0x136/frame 0xfffffe349829abb0
> fork_exit() at fork_exit+0x84/frame 0xfffffe349829abf0
> fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe349829abf0
> --- trap 0, rip = 0, rsp = 0xfffffe349829acb0, rbp = 0 ---
> KASSERT failed: uma_zalloc_arg(M_WAITOK) in no_sleeping context
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe349829a2d0
> kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe349829a380
> _kassert_panic() at _kassert_panic+0xd7/frame 0xfffffe349829a400
> uma_zalloc_arg() at uma_zalloc_arg+0x6c5/frame 0xfffffe349829a470
> malloc() at malloc+0x1c7/frame 0xfffffe349829a4c0
> g_post_event_x() at g_post_event_x+0x84/frame 0xfffffe349829a510
> g_post_event() at g_post_event+0x5d/frame 0xfffffe349829a580
> adacleanup() at adacleanup+0x62/frame 0xfffffe349829a5a0
> cam_periph_release_locked_buses() at cam_periph_release_locked_buses+0xde/frame 0xfffffe349829aaa0
> cam_periph_release_locked() at cam_periph_release_locked+0x1b/frame 0xfffffe349829aac0
> adadone() at adadone+0x26e/frame 0xfffffe349829ab20
> xpt_done_process() at xpt_done_process+0x3a4/frame 0xfffffe349829ab60
> xpt_done_td() at xpt_done_td+0x136/frame 0xfffffe349829abb0
> fork_exit() at fork_exit+0x84/frame 0xfffffe349829abf0
> fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe349829abf0
> --- trap 0, rip = 0, rsp = 0xfffffe349829acb0, rbp = 0 ---
> (ada3:ahcich3:0:0:0): Periph destroyed


-- 
Regards,
Bryan Drewery

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