diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2018-10-11 12:38:27 +0200 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-12-16 22:09:41 +0000 |
| commit | 4f78f1df7fc63b55a6e9fe9184f2d156aeac32c9 (patch) | |
| tree | a6cc22e7347fc91d61eb821b726f0724ea7f8c85 /arch/x86/include | |
| parent | b427832009b97a3ee412ef643a80b15372a7754d (diff) | |
x86/percpu: Fix this_cpu_read()
commit b59167ac7bafd804c91e49ad53c6d33a7394d4c8 upstream.
Eric reported that a sequence count loop using this_cpu_read() got
optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
because the interface is IRQ-safe, therefore an interrupt can have
changed the per-cpu value.
Fixes: 7c3576d261ce ("[PATCH] i386: Convert PDA into the percpu section")
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Cc: hpa@zytor.com
Cc: eric.dumazet@gmail.com
Cc: bp@alien8.de
Link: https://lkml.kernel.org/r/20181011104019.748208519@infradead.org
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/percpu.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index 851bcdc5db04..83ad4424d711 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -185,22 +185,22 @@ do { \ typeof(var) pfo_ret__; \ switch (sizeof(var)) { \ case 1: \ - asm(op "b "__percpu_arg(1)",%0" \ + asm volatile(op "b "__percpu_arg(1)",%0"\ : "=q" (pfo_ret__) \ : constraint); \ break; \ case 2: \ - asm(op "w "__percpu_arg(1)",%0" \ + asm volatile(op "w "__percpu_arg(1)",%0"\ : "=r" (pfo_ret__) \ : constraint); \ break; \ case 4: \ - asm(op "l "__percpu_arg(1)",%0" \ + asm volatile(op "l "__percpu_arg(1)",%0"\ : "=r" (pfo_ret__) \ : constraint); \ break; \ case 8: \ - asm(op "q "__percpu_arg(1)",%0" \ + asm volatile(op "q "__percpu_arg(1)",%0"\ : "=r" (pfo_ret__) \ : constraint); \ break; \ |