On Sat, Nov 11, 2023 at 01:31:01AM -0500, matoro wrote: > Hi Helge, I have bisected a regression in 6.6 which is causing userspace > segfaults at a significantly increased rate in kernel 6.6. There seems to > be a pathological case triggered by the ninja build tool. The test case I > have been using is cmake with ninja backend to attempt to build the nghttp2 > package. In 6.6, this segfaults, not at the same location every time, but > with enough reliability that I was able to use it as a bisection regression > case, including immediately after a reboot. In the kernel log, these show > up as "trap #15: Data TLB miss fault" messages. Now these messages can and > do show up in 6.5 causing segfaults, but never immediately after a reboot > and infrequently enough that the system is stable. With kernel 6.6 I am > completely unable to build nghttp2 under any circumstances. > > I have bisected this down to the following commit: > > $ git bisect good > 3033cd4307681c60db6d08f398a64484b36e0b0f is the first bad commit > commit 3033cd4307681c60db6d08f398a64484b36e0b0f > Author: Helge Deller <deller@xxxxxx> > Date: Sat Aug 19 00:53:28 2023 +0200 > > parisc: Use generic mmap top-down layout and brk randomization > > parisc uses a top-down layout by default that exactly fits the generic > functions, so get rid of arch specific code and use the generic version > by selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT. > > Note that on parisc the stack always grows up and a "unlimited stack" > simply means that the value as defined in > CONFIG_STACK_MAX_DEFAULT_SIZE_MB > should be used. So RLIM_INFINITY is not an indicator to use the legacy > memory layout. > > Signed-off-by: Helge Deller <deller@xxxxxx> > > arch/parisc/Kconfig | 17 +++++++++++++ > arch/parisc/kernel/process.c | 14 ----------- > arch/parisc/kernel/sys_parisc.c | 54 > +---------------------------------------- > mm/util.c | 5 +++- > 4 files changed, 22 insertions(+), 68 deletions(-) > > I have tried applying ad4aa06e1d92b06ed56c7240252927bd60632efe ("parisc: Add > nop instructions after TLB inserts") on top of 6.6, but it does NOT fix the > issue. > > Let me know if there is anything I can answer on this. I can provide full > remote access with BMC if it would help. Thanks for the regression report. I'm adding it to regzbot: #regzbot ^introduced: 3033cd4307681c -- An old man doll... just what I always wanted! - Clara
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