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drm/amdgpu: use atomic operation to achieve lockless serialization

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In amdgpu_seq64_alloc there is a possibility that two difference cores
from two separate NODES can try to and could get the same free slot.
So this fixes that race here using atomic test_and_set clear operations.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 4d50a14d346141e03a7c3905e496d91e048bc30c)
This commit is contained in:
Sunil Khatri 2026-05-14 12:31:00 +05:30 committed by Alex Deucher
parent a1d4b228e3
commit 0978406224
1 changed files with 8 additions and 5 deletions
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13
drivers/gpu/drm/amd/amdgpu/amdgpu_seq64.c
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@ -175,11 +175,14 @@ int amdgpu_seq64_alloc(struct amdgpu_device *adev, u64 *va,
{
unsigned long bit_pos;
bit_pos = find_first_zero_bit(adev->seq64.used, adev->seq64.num_sem);
if (bit_pos >= adev->seq64.num_sem)
return -ENOSPC;
for (;;) {
bit_pos = find_first_zero_bit(adev->seq64.used, adev->seq64.num_sem);
if (bit_pos >= adev->seq64.num_sem)
return -ENOSPC;
__set_bit(bit_pos, adev->seq64.used);
if (!test_and_set_bit(bit_pos, adev->seq64.used))
break;
}
*va = bit_pos * sizeof(u64) + amdgpu_seq64_get_va_base(adev);
@ -205,7 +208,7 @@ void amdgpu_seq64_free(struct amdgpu_device *adev, u64 va)
bit_pos = (va - amdgpu_seq64_get_va_base(adev)) / sizeof(u64);
if (bit_pos < adev->seq64.num_sem)
__clear_bit(bit_pos, adev->seq64.used);
clear_bit(bit_pos, adev->seq64.used);
}
/**