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| author | Jordan Niethe <jniethe5@gmail.com> | 2023-08-29 10:12:01 +1000 |
|---|---|---|
| committer | Alexey Kardashevskiy <aik@ozlabs.ru> | 2023-09-18 18:20:45 +1000 |
| commit | dd4d4ea0add97df078d571b48192adaf7c4b0d87 (patch) | |
| tree | a4dbaadf652c32716f3e7583d260cca6c045ffed | |
| parent | 63b66a5147069bda815989732442cb07790609db (diff) | |
| download | SLOF-dd4d4ea0add97df078d571b48192adaf7c4b0d87.zip SLOF-dd4d4ea0add97df078d571b48192adaf7c4b0d87.tar.gz SLOF-dd4d4ea0add97df078d571b48192adaf7c4b0d87.tar.bz2 | |
virtio-serial: Do not close stdout on quiesce
Commit 76fee95 ("slof: Only close stdout for virtio-serial devices")
says that commit cf28264 ("virtio-serial: Rework shutdown sequence")
fixed a hang. The problem was believed to be that it was necessary to
close stdout to shutdown the underlying virtio device.
Commit cf28264 ("virtio-serial: Rework shutdown sequence") closed stdout
on quiesce. This meant when prom_init() called write on stdout after
quiesce, there is a use after free so this is unreliable, and can also
hang (especially after reboots).
Quiescing is intended to put hardware into a safe state for the client
to take over. It is incorrect for SLOF to close ihandles that the client
could still be using, even after a quiesce.
Rather than closing the stdout device, all that needs to happen is to
ensure virtio-serial-shutdown gets called. On quiesce, close the virtio
device, but leave the stdout device itself open.
Commit 8174acd ("virtio-serial: Close device completely") handles reads
and writes as no-ops if the underlying virtio device is closed so there
is no problem with the client calling "write" on stdout after this, but
no output will be displayed.
Fixes: cf28264 ("virtio-serial: Rework shutdown sequence")
Debugged-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
Co-developed-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
Signed-off-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
| -rw-r--r-- | board-qemu/slof/virtio-serial.fs | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/board-qemu/slof/virtio-serial.fs b/board-qemu/slof/virtio-serial.fs index 41e2e04..de42cc7 100644 --- a/board-qemu/slof/virtio-serial.fs +++ b/board-qemu/slof/virtio-serial.fs @@ -33,16 +33,14 @@ virtio-setup-vd VALUE virtiodev : virtio-serial-term-key? virtiodev virtio-serial-haschar ; : virtio-serial-term-key BEGIN virtio-serial-term-key? UNTIL virtiodev virtio-serial-getchar ; -: virtio-serial-close-stdout s" stdout" get-chosen IF decode-int nip nip close-dev THEN ; - \ Basic device initialization - which has only to be done once : init ( -- ) virtiodev virtio-serial-init drop TRUE to initialized? - \ Linux closes stdin at some point in prom_init(). This internally triggers a - \ quiesce in SLOF. We must ensure stdout gets closed as well otherwise the - \ device cannot be reset properly and the boot will hang. - ['] virtio-serial-close-stdout add-quiesce-xt + \ virtiodev must be shutdown at quiesce so the device is reset properly. + \ The read and write methods can be called after quiesce so must handle + \ virtiodev being closed. + ['] shutdown add-quiesce-xt ; 0 VALUE open-count @@ -62,8 +60,8 @@ virtiodev virtio-serial-init drop open-count 0> IF open-count 1 - dup to open-count 0= IF shutdown THEN + close THEN - close ; : write ( addr len -- actual ) |