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mm/memory-failure.c: support use of a dedicated thread to handle SIGBUS(BUS_MCEERR_AO)

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Currently memory error handler handles action optional errors in the
deferred manner by default.  And if a recovery aware application wants
to handle it immediately, it can do it by setting PF_MCE_EARLY flag.
However, such signal can be sent only to the main thread, so it's
problematic if the application wants to have a dedicated thread to
handler such signals.

So this patch adds dedicated thread support to memory error handler.  We
have PF_MCE_EARLY flags for each thread separately, so with this patch
AO signal is sent to the thread with PF_MCE_EARLY flag set, not the main
thread.  If you want to implement a dedicated thread, you call prctl()
to set PF_MCE_EARLY on the thread.

Memory error handler collects processes to be killed, so this patch lets
it check PF_MCE_EARLY flag on each thread in the collecting routines.

No behavioral change for all non-early kill cases.

Tony said:

: The old behavior was crazy - someone with a multithreaded process might
: well expect that if they call prctl(PF_MCE_EARLY) in just one thread, then
: that thread would see the SIGBUS with si_code = BUS_MCEERR_A0 - even if
: that thread wasn't the main thread for the process.

[[email protected]: coding-style fixes]
Signed-off-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Tony Luck <[email protected]>
Cc: Kamil Iskra <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Chen Gong <[email protected]>
Cc: <[email protected]>	[3.2+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Naoya Horiguchi 2014-06-04 16:11:02 -07:00 • committed by Linus Torvalds
commit 3ba08129e3
2 changed files with 48 additions and 13 deletions
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5
Documentation/vm/hwpoison.txt
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@ -84,6 +84,11 @@ PR_MCE_KILL
PR_MCE_KILL_EARLY: Early kill
PR_MCE_KILL_LATE: Late kill
PR_MCE_KILL_DEFAULT: Use system global default
Note that if you want to have a dedicated thread which handles
the SIGBUS(BUS_MCEERR_AO) on behalf of the process, you should
call prctl(PR_MCE_KILL_EARLY) on the designated thread. Otherwise,
the SIGBUS is sent to the main thread.
PR_MCE_KILL_GET
return current mode