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py/gc: Make gc_lock_depth have a count per thread. - #7238
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Should fix #6957. |
This commit makes gc_lock_depth have one counter per thread, instead of one global counter. This makes threads properly independent with respect to the GC, in particular threads can now independently lock the GC for themselves without locking it for other threads. It also means a given thread can run a hard IRQ without temporarily locking the GC for all other threads and potentially making them have MemoryError exceptions at random locations (this really only occurs on MCUs with multiple cores and no GIL, eg on the rp2 port). The commit also removes protection of the GC lock/unlock functions, which is no longer needed when the counter is per thread (and this also fixes the cas where a hard IRQ calling gc_lock() may stall waiting for the mutex). It also puts the check for `gc_lock_depth > 0` outside the GC mutex in gc_alloc, gc_realloc and gc_free, to potentially prevent a hard IRQ from waiting on a mutex if it does attempt to allocate heap memory (and putting the check outside the GC mutex is now safe now that there is a gc_lock_depth per thread). Signed-off-by: Damien George <[email protected]>
The RP2040 has 2 cores and supports running at most 2 Python threads (the main one plus another), and will raise OSError if a thread cannot be created because core1 is already in use. This commit adjusts some thread tests to be robust against such OSError's. These tests now pass on rp2 boards. Signed-off-by: Damien George <[email protected]>
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This is an alternative to #7217.
This PR makes gc_lock_depth have one counter per thread, instead of one global counter. This makes threads properly independent with respect to the GC, in particular threads can now independently lock the GC for themselves without locking it for other threads. It also means a given thread can run a hard IRQ without temporarily locking the GC for all other threads and potentially making them have MemoryError exceptions at random locations (this really only occurs on MCUs with multiple cores and no GIL, eg on the rp2 port).
The PR also removes protection of the GC lock/unlock functions, which is no longer needed when the counter is per thread (and this also fixes the cas where a hard IRQ calling gc_lock() may stall waiting for the mutex).
It also puts the check for
gc_lock_depth > 0outside the GC mutex in gc_alloc, gc_realloc and gc_free, to potentially prevent a hard IRQ from waiting on a mutex if it does attempt to allocate heap memory (and putting the check outside the GC mutex is now safe now that there is a gc_lock_depth per thread).