Messages in this thread | | | Subject | Re: [PATCH v2] firmware: fix sending -ERESTARTSYS due to signal on fallback | From | Martin Fuzzey <> | Date | Fri, 9 Jun 2017 09:40:47 +0200 |
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On 09/06/17 03:57, Luis R. Rodriguez wrote: > On Thu, Jun 8, 2017 at 6:10 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote: >>> Android didn't send the signal, the kernel did (SIGCHLD). >>> >>> Like this: >>> >>> 1) Android init (pid=1) fork()s (say pid=42) [this child process is totally >>> unrelated to firmware loading] >>> 2) Android init (pid=1) does a write() on a (driver custom) sysfs file which >>> ends up calling request_firmware() kernel side >>> 3) The firmware loading fallback mechanism is used, the request is sent to >>> userspace and pid 1 waits in the kernel on wait_* >>> 4) before firmware loading completes pid 42 dies (for any reason - in my >>> case normal termination) > Martin just to be clear, by "normal case termination" do you mean > completing successfully ?? Ie the firmware actually did make it onto > the device ?
The firmware did *not* make it onto the device since the request_firmware() call returned an error (the code that would have transfered it to the device is only executed following a successful request_firmware)
The process that terminates normally is unrelated to firmware loading as I said above.
The only things that matter are: - It is a child process of the process that calls request_firmware() - It terminates *while* the the wait_ is still in progress
Here is a way of reproducing the problem using the test_firmware module (which I only just saw) on normal linux with no Android or custom driver
#!/bin/sh set -e
# Make sure the system firmware loader doesn't get in the way /etc/init.d/udev stop
modprobe test_firmware
DIR=/sys/devices/virtual/misc/test_firmware
echo 10 >/sys/class/firmware/timeout; sleep 2 & echo -n "/some/non/existing/file.bin" > "$DIR"/trigger_request;
If run with the "sleep 2 &" it terminates after 2 seconds If the sleep is commented it runs for the expected 10 seconds (the firmware loading timeout)
Since the sleep process is a child of the script process requesting a firmware load its death causes a SIGCHLD causing request_firmware() to abort prematurely.
Martin
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