See my comments inline below.
Regards,
Zhanjun Dong
On 2025-08-20 6:17 a.m., Andi Shyti wrote:
Hi Zhanjun,
On Tue, Aug 19, 2025 at 12:00:10PM -0400, Zhanjun Dong wrote:
Boolean flag access from interrupt context might have synchronous issue on
/synchronous/synchronization/
/issue/issues/
multiple processor platform, flage modified by one core might be read as an
/flage/flags/
old value by another core. This issue on interrupt enable flag might causes
interrupt missing or leakage.
/missing/misses/
Fixed by change the data type as automic to add memory synchronization.
This can be re-written: "Change the interrupts.enable type to
atomic to ensure memory synchronization."
Will follow all above comments
Fixes: a187f13d51fa0 ("drm/i915/guc: handle interrupts from media GuC")
What issue are you exactly trying to fix? And have you tested
Will add:
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14834
that this patch is this really fixing it? Where is the flag's
CI report this issue about every 1 or 2 months and close it because no
reproduce.
I can reproduce it in about 1000 rounds(about 9 hours) of IGT test but
not at 100% rate, so it is hard to say really fixed because of hard to
reproduce.
My latest test runs 2200 rounds in total has no reproduce.
misalignment happening?
Please remember that when in interrupt context you are already
running in atomic, so that probably you don't need to have an
additional atomic access to variables.
Interrupt context only read it. When the flag was changed and interrupt
was triggered in very short time, the flag read at interrupt context
might read out old value, if other core(non interrupt context) set the
flag and ISR read out 0, ISR will do simple return and misses interrupt
handling, making it appear as lost interrupt; if other core clear the
flag and ISR read out 1, ISR will continue to run and not stop as
expected, making it appear as an interrupt leak. >
Andi
Signed-off-by: Zhanjun Dong <zhanjun.d...@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospu...@intel.com>
